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