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