Here is the full list of all 14 Weapon of Choice achievements.
Rescue every Solus Operative.
Shoot 5 birds.
Rescue someone and get them out of the level.
Kill 10 aliens while hanging by the SPIDER PACK.
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.