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