Here is the full list of all 26 My Pet Rock achievements.
Surely you're still learning to play right?
Cool Name!
This isn't really a rock anymore!
Won a Prize from the Slot Machine 25 Times
Unlocked the Janitor!
Killed 10000 Enemies
Unlocked the Lawyer!
Beat the Game Using Russian Roulette
Beat the Game Using Eye for an Eye
Beat the Game Using Elitist
Beat the Game using WMD
Or is it...?
Killed 50 Bosses
Unlocked the Scientist!
Killed 100 Enemies using fire
Killed 25 Bosses
Unlocked the Task Force!
Unlocked the Farmer!
Killed 10 Bosses
Unlocked the Miner!
Killed 1000 Enemies
Fully upgraded the rock
Killed 500 Enemies
Unlocked the Citizen!
Unlocked the Engineer!
Beat the Game Using Survival Mode