What are some good hobbies for a guy to have?

Brewing your own beer. Combine your alcoholism with something productive. Its a win win!

Healthy Cooking, Biking and Trading Stocks

Good cooking will keep you well fed and get you laid.

Biking will keep you in shape.

Trading Stocks will keep you sharp and make you some money.

I would like to say that all of the other suggestions are great too.

Don't pick anything "to pick up chicks." That being said, here's some manly hobbies:
Hunting/Fishing, Backpacking, Jazz Guitar (boys play "guitar," men play a style of music), Brewing, Carpentry, Boxing, Cooking.

With Kraig on the brewing your own beer. Also enjoy keeping busy with different sports. Lately it has been racquet ball for me and my friends.

Cooking, road/mountain biking, running, video games and photography.

Mountain biking, baseball, pyrotechnics, and lots of projects. If nothing in your house is broken or needs improvement, then find some kids in the neighborhood and build a catapult or trebuchet with them...you get to "prepare for the apocalypse" (nice, Javier) while teaching them the laws of physics and hopefully launching a flaming piano several hundred yards.

Not necessarily "guy" hobbies, but here goes:

Motorcycle riding/racing/customizing
Car racing/restoring/customizing
Photography/Videography
Traveling (international if possible)
Exercise (gym, outdoor sports, rec. sports leagues, etc.)
Art (paint, digital, sculptures, etc.)

Shooting rats at the dump.

Cooking
Playing a musical instrument
Something that constitutes exercise
Reading (books or magazines that make you think, e.g. The Economist, The New Yorker, The Atlantic, etc)

Cooking, nothing is as satisfing as preparing a meal as good (or better) than a good restuarant.
Classic cars: I personally enjoy Italian cars, reasonable in cost(think Alfa Romeo and Fiat) and very unique.
Skiing or Snowboarding: if you are near the mountains)
Playing poker: kinda cliche, I know, but poker is an activity almost exclusively enjoyed by men, it CAN be cheap, and it involves and good deal of mental skill)

Internet debating.

Definitely brewing beer. It gives you a certain swagger with your friends.

These are mine, your mileage may vary:

Cooking - women love it when the guy cooks, and outside of really nice places, I can do better in my own kitchen for way cheaper...

Martial Arts - It's great for stress reduction AND self-confidence, pretty much whatever style suits your personality

Carpentry - I like getting into the garage and actually creating tangible things (as opposed to my real job in IT where it's all very abstract), my boys like getting sawdusty, win all around

Flying planes... Women love pilots... and if you go far enough and become an ATP at the airlines... you wont have to say this to your son:
"Son, someday you will make girl very happy, for a short period of time. Then she'll leave you and be with new men who are ten times better than you could ever hope to be. These men are called pilots."

Woodworking. Relaxing, invigorating, challenging, and dangerous. Just the right kind of hobby. Everything (tools and books) you need to get started can be found at "Shelter": http://www.shelterinstitute.com/catalog/index.php?cPath=2&osCsid=4e5a2b505c71b43465e2e020c7998209

Crossfit, cycling, or martial arts for fitness

Something creative with your hands - like painting, woodworking, etc...

Read voraciously and don't waste your time on junk.

Anything that you can enjoy without worrying what others will think of you for enjoying it is a good choice for a hobby. Pick something you can indulge in often, so that even on your most stressful day it can be there for you to look forward to.

Cooking, Knitting, Snowboarding, Video Games, Art Making

Social dancing. It's cheap, great exercise, lots of fun, a great way to meet people, and you can do it everywhere where you go--all you need is a pair of shoes. It's also a good skill to have in your grownup toolbox.

I like swing dancing, but I've heard great things about salsa and tango.

I started fly fishing 55 years ago when I was 6....do the math. I never stopped and it has become more than a hobby, but at it's base is something far beyond any hobby notion. I really don't like the idea of hobbies. Hobbies remind me of dilettantes... I prefer obsessions. When I think of hobbyists I think of old guys in cardigans peering through magnifying glasses at ancient stamps..that kind of thing. I fish almost 200 days a year and then some if the weather is right. My current obsession is using a newly purchased Hammerhead sled on the wooded trails above my cabin. Hobbies are for merit badges and book discussion groups. Get outside!

Rather than provide you a litany of hobbies in which you may or may not be interested, I'd rather like you to think about pursuits that would round out your own personality.

Think about the quintessential Renaissance Man (not the Danny Devito movie; that sucked.) You want to find hobbies that express different facets of your being. For example, if someone said their hobbies were "Boxing, beer, NFL, Ultimate Fighting," you would probably think "Meathead." In contrast, "Brazilian Jiujitsu, interior decorating, snowboarding, and 18-century poetry" would make you think "Now that sounds like an interesting fella."

Now don't choose things just because they sound good - that doesn't work either. Look for hobbies in a wide variety of categories - literature, art, sports, the outdoors, movies - that make you seem like the well-rounded person you probably are.

Competitive IPSC pistol shooting, woodworking, gym, frequent naps

I'm 62 and naps thke up the least of my time.

First of all great question, second of all great answers (I picked up some good ideas)

Train for a marathon! I joined Team in Training, which is a group that helps your train for a endurance event. TNT supports the Leukemia & Lymphoma Society, and all participants raise money that goes directly to the charity. It has been a tremendously rewarding experience that I would recommend to anyone! check out there website "Team-in-Training"http://www.teamintraining.org/

and yes if you care chicks dig a guy who is running a marathon to save lives...and most of your teammates are females...

Cooking. Running. Tearing it up!

You should care less about what other people think of whatever it is you do, and think about in what ways it can positively effect your life.. for instance if you were leading an unhealthy lifestyle, taking up Kayaking or Canoeing, or as mentioned before training for a road race could be a great idea.

If you spend your time at a job that is boring and monotonous, maybe try to tap into your creative side with painting, learning an instrument, carving wood, or graphic design.

Chances are basically for anything you can dream of there is probably a group of people who are already involved in the activity in your community.

One thing no one has yet to mention here that I think is a really great 'hobby' if you have some time and some space is gardening. Getting outside, getting your hands dirty, and enjoying the product of your work really is amazing. Like many of the other hobbies mentioned above, gardening is one that you can always grow with (pun intended) and even share with others.

A couple other random ideas that I haven't seen mentioned, learning to play Chess, and stained glass (cutting things with diamond-edged saws is always cool).

Having sex with women.

Target shooting. Start with a .22 caliber and move up calibers from there until you're uncomfortable firing 100 rounds. I like using a 9mm, personally. Fire 100 9mm rounds, and you'll feel fantastic.

If you can afford it and live on the coast, sailing. Try and get a friend with a boat to take you out and see if you like it.

Kiteboarding/Snowkiting! Its the ultimate sport, cruse over the water or snow and boost yourself 40+ft in the air whenever you please.

Be Warned- This sport takes over your life.

Anything that keeps you away from uncrate! this page is so addicting, that it takes up all of my time (and money)...

I'm prepared for the Zombie Apocalypse, and I create art. What more does a guy need for a hobby?

carpentry and racquetball give deep satisfaction when i can spare a moment. i get to draw all day for work, but that can be a tremendous hobby as well.

Yoga.

ping pong, billiards - neither require any athletic ability

Smashing bottles behind a WaWa.

Firstly, have as many hobbies as you can afford, or as many peak your interest - it will make you a more rounded person by exposing you to different groups of people within the realm of a given hobby. Do something strictly for your interest alone. Hobbies are "you" time. Beyond that, have fun and experiment with potential interests by lurking on online forums before spending loads of cash on something you won't be in to.

Fishkeeping!

Disc golf and bocce ball during the summer.
Drinking whiskey and reading books during the winter.

Small scale wood turnings. Specifically, making your own pens. The initial investment is relatively modest, does not require significant space, and allows you to create very unique items for yourself as well to use as gifts.

mopeds, those classic ones from the 70s and 80s that had bicycle pedals on them. There cheap, easy to customize and even for someone with little or no mechanical experience, they're pretty easy to figure out.

Building anything out of anything.
Collecting and smoking great cigars.
Playing pool or poker
Playing an instrument (other than girlie ones like the clarinet)
Taking MMA classes
Paintball

motorcycle racing,cooking,dismantling stuff and forgeting how to put them back togheter,alternative photography printing,(since digital came along trying this is a lot easier,especially anything involviong contact printing).
i also like traveling to obscure places(think a small village in the middle of nowhere)
and the list keeps growing/changing but these have been with me through sometimes
btw start doing something that YOU like,not women not friends etc .when everything else is gone your passions are what will keep you going mentally

A good hobby for anyone is to volunteer your time/services to a non profit or charitable organization. You will not only be helping someone, you will get a lot of gratification and that all important KARMA!

Buy an acoustic guitar. Learn the G, C and D chords. You can now play several thousand songs. Now go find a campfire and start singing.

Learn how to sharpen knives. There are tons cooks, survialist, and knife-collectors out there that will pay you.

I would say there's nothing more satisfying than whittling. All you need is a good knife and some nice hardwood and a cold brew, and at the end of it (once you've mastered the technique, a process that is both rewarding and inexpensive) you have timeless art that you can be proud of.

Martial Arts, Shooting, a few good Magic tricks, Knife throwing, Survival Skills, Racing, Some kind of crafting like wood-working or mechanics or welding.

Frisbee Golf (aka Disc Golf) is a great sport. Low barrier to entry - most courses are free - and if you know how to throw a frisbee you can play it. Also gets you outside with friends and away from obligations.

No Doubt Hunting/Fishing/Outdoor exploring for me. I have been an outdoors addict since I was less than a year old. Nothing puts you in tune more with the ways of the world than becoming a predator in the wild. Today's enviromentalist has nothing on a true outdoorsman. Nothing tunes your senses better either, its almost impossible to explain, but any other passionate outdoorsman knows exactly what I'm talking about. Also learn to cook your bounty with flair and it will pay divendends. My wife finds it sexy when I make a gourmet meal from something that I hunted down and killed myself. It adds a suaveness to counter the macho barbarian. Learning a thing or two about interior design is also helpfull. Lately I have also taken up reading on more serious subjects as I am trying to become a rounded gentleman. The next two on the list are "Wealth of Nations" and "De Officiis"