Heal yourself plus 5 other players with one grenade

In Co-op Mode, Use Syringe on Yourself 100 Times.

Beat Moonbase on Normal Difficulty

Hold dual 9mm, dual hand cannons and Dual Revolvers

As Demolitions, kill 1000 Specimens with the Pipebomb.

Kill 1000 Hillbilly Zeds

Kill 1000 Specimens with the SCAR.

Kill 100 Fleshpounds with the AA12.

Kill 10 Circus Clots with a Fire-based weapon.

Kill 10 Halloween zeds in explosions using the Seeker 6 or the M32 within 5 seconds

Kill 12 clots with one magazine without reloading (MK23)

Kill 12 zeds with a full magazine from the Combat Shotgun

Kill 15 Hillbilly Crawlers in 1 game with the Tommy Gun or MKb42

Kill 15 Husks with the Husk Cannon

Kill a Hillbilly Husk and another Hillbilly Zed in the same shot with the Buzzsaw Bow or M99

Kill 1 specimen ONLY while expending a full M4 Assault Rifle magazine

[2010 Xmas] Kill 20 Christmas Clots in one wave.

Kill 20 crawlers in mid-air with the M79.

Kill 250 Halloween Specimens in Bedlam

Kill 25 Halloween Scrakes in Bedlam

Kill 2 scrakes with one shot (M99)

Kill 2 Circus Stalkers with a Melee weapon to the back in one wave.

[2010 Xmas] Kill 3 Christmas Bloats with the Bullpup in one wave.

[2010 Xmas] Kill 3 Christmas Stalkers with a Lever Action Rifle without reloading.