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