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