You gain access to the Feats of Prowess of Weapons at level 10.
Particular feats are different for each weapon and the game has several different types of weapons that cater to different play styles.
Rifles, Submachine Guns, Heavy Weapons and Sniper Rifles are good for people used to playing first person shooters as they usually have: X amount of kill, X amount of headshots and X amount of kills with each mod equipped; as their feats, although the (Heavy Weapon) Deep Freezer is different in that it has feats for inflicting damage with the weapon as well as shattering enemies with your knife after freezing them instead of kills and headshots.
If you have difficulty gaining headshots, you may prefer Shotguns as they need close kills instead; though you have to be more or less right next to the enemy when you gain the kill. Launchers are good for people that prefer ambush attacks and need muti-kills instead of headshots.
If enjoy playing Medic you may find that the Motivator is a good weapon to use for this as it doesn't require any kills (as you can't do damage with it) or mods (there are none), just healing. Although the feat to gain 1200 healing in 10 seconds will take teamwork, as you will more than likely need to heal 3 to 4 players using the Mighty body type while they are under constant fire.