Medal of Honor

The classes are Rifleman, Special Ops, and Sniper. Play each class for two minutes in a multiplayer game. You can get this easy in one match.

The best game mode to attempt this achievement on is Team Assault as this generally is the game mode with the longest matches. When you join the match, wait for the next match if you join halfway through the match. At the start of the match, start with your best class as you will get most kills with this, adding to your experience of that class. Aim to time yourself for 2 minutes and then when you are killed, choose the next class. After another 2 minutes, choose the final class and after 2 minutes of the final class, the achievement should come up.