Here is the full list of all 42 Gunscape achievements.
Create your first map
Publish your first map
Play your first Free-For-All DeathMatch game
Play your first Team DeathMatch game
Play your first Team Capture-The-Flag game
Play your first Gun Game game
Play your first Infection game
Kill a robot boss
Kill a dinosaur boss
Play your first split-screen game
Place your first block in Build mode
Place 100 blocks in Build mode
Place 10,000 blocks in Build mode
Place a Checkpoint in your map
Place a flag in your map
Rate another player's map as good
Rate another player's map as bad
Finish the first Blowfish campaign map
Finish the Blowfish campaign
Build a multi-map campaign map
Kill an enemy player
Kill 1,000 players
Kill 50 players with the Speargun tripwire
Kill 500 players with the Gauss Rifle
Use the Freezethrower to slide 3 blocks
Kill 1,000 players with the PFG
Kill 50 players with your Fists
Kill 500 players with the Dual Zhotguns
Kill 5 players with a knife
Kill 100 players with the ID Disc
Kill 100 players with the Flamethrower
Kill 1000 players with the E-Bow
Win 50 Deathmatch games
Win 25 CTF games
Win 25 Infection games
Won 25 Survival games
Program 5 Terminals
Steal 25 flags in CTF
Return 25 flags in CTF
Killed yourself 50 times
Kill 100 AI enemies
Kill 5,000 AI enemies