Here is the full list of all 63 Gunslugs achievements.
Complete mission 5.3
Complete mission 5.2
Complete mission 5.1
Complete mission 4.3
Complete mission 4.2
Complete mission 4.1
Complete Hell with BA
Complete Hell with Sarge
Kill 5 skulls in one mission
Destroy 5 hell tanks in one game
Blowup a death worm
Kill a flying fire skull
Rescue Sarge
Score 2500 points
Find the sketch world!
Drive over 10 dudes with a tank
Drive over 5 dudes with a tank
Kill a chicken, and spread some eggs!
Rescue B.A. Baracuda
Complete mission 3.3
Complete mission 3.2
Complete mission 3.1
Complete mission 2.3
Collect 175 coins in one game
Destroy four mechballs
Chain explosion of 3
Score 2000 points
Get your train ticket and ride.. or run
Kill 50 guys in one mission
Blow up 4 dudes at once
Chain explosion of 2
Grab energy drink
Score 1000 points
Collect 150 coins
Locate the arcade !
Kill 10 guys with grenades
Take a jetpack ride
Rescue Sonya
Kill 20 guys
Find "a" princess
Complete mission 2.2
Drive a tank
Rescue Willis KiYay
Change the tune using a jukebox
Collect 125 coins in one game
Rescue Sly Rocko
Score 500 points
Complete mission 2.1
Kill 5 guys from cover
Complete mission 1.3
Air kill a dude
Find the voodoo priest
Blow up 2 dudes at once
Collect 100 coins
Make a chopper crash
Kill 10 guys in a mission
Complete mission 1.2
Complete mission 1.1
Collect 75 coins
Grab a new weapon
Complete bootcamp
Deactivate your first beacon
Take cover rookie!