Here is the full list of all 14 Weapon of Choice achievements.
Shoot 5 birds.
Rescue someone and get them out of the level.
Kill 10 aliens while hanging by the SPIDER PACK.
Rescue every Solus Operative.
Beat all branches.
Beat the Evil Sun.
Beat level 1 (Mountain Village) in under 1 minute and 10 seconds.
Collect all MBG pies.
Use Xerxes to reach a boss without touching the ground.
Use the SMOKE WALK for the maximum time.
Kill 10 enemies with the SPIKE LIFT.
Beat a game branch only killing bosses.
Beat a game branch without activating death-brushing.
Beat all branches in MEGA-WICKED difficulty.