Here is the full list of all 17 Tower of Guns achievements.
Reach Endless Stage 14
Accumulate 888 Gold In a Single Run
Tilt 10 Times in a Single Stage
Complete a Stage After Firing Exactly Fourteen Shots
Discover the Secret Code
Complete a Stage without Picking up ANYTHING
Find and Level The Motivator Gun to Level 5
Kill over 350 Mobs in a Single Level
Stomp a Hugbot to Death
Unlock all the Guns
Unlock all the Perks
Pick up 1000 Health Items While at Full Health
Kill That Dang Wall of Turrets Three Times
Jump and Remain Airborn for 45 Seconds
Complete a Stage Without Anything but the Boss dying
Die while a Boss is Exploding
Pick up Four Difficulty++ Badges in a Single Life