What branch is based on personal preferences. I’m going into the Marine Corps, and I’m just a bit younger than you. I have my personal reasons – though I’d probably be better suited for something like the Air Force.
What about you? Tell us about yourself/what you’re looking to do and we can give you suggestions. I can give you a very basic rundown.
Marine Corps: The tough summabitches. The USMC has the most physically and mentally intensive basic training of all branches. Contrary to popular belief, the Marine Corps is not comprised of dimwitted, bloodthirsty animals. Marines hold their pride closer to the chest than any other branch (in my personal opinion, don’t bomb me, Bluefreedom!). MOSes (Military Occupational Specialty, or jobs) range from technical to… well, what you expect. Gruntly. Check out what they offer – not everything is killing or patrol duty. Everything is shared; if you want to live by the military and be encompassed by the esprit de corps, the Marine Corps might be where you want to go.
Highly recommended. By me. :P
Army: Well rounded in all areas. If you’re looking for a nice bonus upon entry, I’d look here. Based on personal experience (word of mouth, I’ve a bunch of buddies in both the Army and Marine Corps), there’s a large chance that you won’t get your desired job. Though their “rules” are more lax, there seems to be a huge, brooding corporate feel to it all. Can you tell I come from a Marine family? haha. Honestly, Army ain’t my thing. I’d talk to someone that can give you good insight there.
Navy: Dependent on what you want to do, the Navy could be a very good choice. They have a ton of technical jobs that directly translate back into the civilian world. If you’d like to see the world and pick up some port-side hookers, the Navy might be what you’re looking for.
Air Force: Possibly THE best branch to join if you’re looking to assimilate back into the civilian world, eventually. With so many technical positions, it’s hard to not find something you’d like to do. Beware, if you want to fly a fighter jet: I hear it’s very difficult to get into the aviation program. Really, if you want to join the military aren’t keen on being treated like a tool, I’d suggest the Air Force. Also, be aware that you’re going to need some high ASVAB scores to gain entry. Bluefreedom has the best information on this, I’d ask him questions on what it’s like.
Now, you obviously want to be in some semblance of good shape prior to being shipped off to Basic. Also to note, if you have college credits, you may qualify for officer school. That’s something you might want to look into.