Every military has their categories of specialties for example the Air cavalry who's main specialty is Helicopters or the Infantry who's main specialty is ground attack. If you were to join your countries military what would you go in for?
I'd go in to try and get into an armored division like the 2nd or 3rd armored or the air cavalry but if I couldn't get into any of those I'd try to get into a Combat engineer role and ship to Fort Wood.
Please don't base your options on games like battlefield and CoD as they usually depict your soldier being a multipurpose soldier. Also many of the things in those games the area doesn't actually do that like snipers, they usually travel in groups of 2, A shooter and a spotter.
Ex: "Lol, I'd want to join so I can 360 n0scope some taliban nubs as a sniper."
Some examples of US roles you can go into:Marksmen
Scout Recon
Corpsmen, Medical personnel
Combat Engineer, AKA "Sappers"
Pilot
Gunner
Infantryman
Airborne
There are four branches of the Military, some examples of what each branch has to offer.
US Army (Infantry, Rangers, Green Berets, Delta Force)
US Marine Corps (Infantry, Force Recon)
US Airforce (Pilots, technicians, chair people, Pararescue, Combat Air Controllers)
US Navy (Sailors, technicians, pilots, sea bees, seals)
The US army and USMC both use the M1A1 and M1A2 Abrams series of tanks, however each branch uses them differently. The Army also has armored vehicles like the M2/M3 Bradley, the Stryker, AMPV. The USMC uses vehicles like the LAV-25, the AAVP7. Both branches operate towed artillery systems and mobile systems like the M270 and M109. The USMC has access to some aircraft like the Harrier, the F-18, soon to be F-35, CH-46, AH-1Z Viper, and the Osprey. The Army operates some aircraft like the AH-64 Apache, UH-60, and CH-47.
The airforce operates aircraft like the F-16, F-15, F-22, A-10, soon to be F-35, all the bombers. The operate from airbases on land. The navy operates from carriers and aircraft like the F-18, F-35, and certain variants of the A-6.
Also, say you have Asthma or currently suffer from depression the Military would not let you in as your medical conditions would hinder you.
Take in mind, Special operation groups like the US army rangers you have to be in the military BEFORE they select you also you must go through a tougher boot camp again and will only accept males so if you Really want to do special operations look at their specifications.