Scout
The job of the scout is more than that of a sniper. You are responsible for setting up targeting sights for artillery as well.

Sea
At sea you are in command of ships, you can control and do battle in subs, battle ships, aircraft carriers, other ships as well as landing craft.

Medic
A medic carries a Sub Machine Gun
and can provide medical care to the wounded solider.

Heavy MG nest
When you get behind the machine gun in a MG nest you can do a lot of damage fast. You need to be careful though or you'll overheat the gun before you know it.

Air
There are quite a few different planes that you can fly in BF1942. Bombers, fighters, and torpedo planes are the main roles. 
Although the flight sim part of BF is really pretty lousy it's still a favorite of most players.