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