Here is the full list of all 13 Girls Guns and Zombies achievements.
Reach Title Screen
Kill 50 Enemies
Kill 150 Enemies
Kill 500 Enemies
Perform 50 Headshots
Gain 25 Fun
Scavenge 50 Resources
Lose 50 pieces of Clothes
Clear 5 Waves in Survival
Complete 100 Races
Win 50 Races