Here is the full list of all 42 Gunpoint achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Chicken out of telling Katie the truth at the last minute.
Beat Fritz Gessler to death.
Slam Fritz Gessler's office door into him.
Shoot Fritz Gessler.
Defeat Gessler by rewiring his gun.
Kick Fritz Gessler's office door into him.
Notice the story doesn't necessarily gel with the mechanics. Become qualified games journalist.
Free an innocent man at the expense of catching a guilty one.
Steal Gessler's technology for Rooke.
Create a custom mission with at least one objective.
Mock the chief of police at a critical moment.
Jump into an Enforcer to knock him through a window.
Knock Fritz Gessler out of his office window.
Use the Longshot to make a guard unintentionally shoot another (outside of the test lab).
Complete a mission faster than I can.
Upgrade your battery capacity to the non-figurative max.
Upgrade your Bullfrog Hypertrousers to pounce instantly.
Publish your personalised epilogue.
Complete the game.
Knock Fritz Gessler out with a punch.
Intimidate Fritz Gessler into surrendering.
Get knocked down by an opening door.
Catch a guilty man at the expense of freeing an innocent one.
Use the Gatecrashers to kick a door through a window.
Use the Gatecrashers to kick a door into a guard.
Use the Gatecrashers to kick a door off its hinges.
Use the Prankspasm to knock out someone who isn't standing near a power socket (outside of the test lab).
Upgrade your Bullfrog Hypertrousers to maximum jump strength.
Tell Gessler that Rooke's hired you to betray him.
Complete the police chief's missions without incriminating yourself.
Complete a mission that has guards with no violence, witnesses or loud noises.
Use no violence at all on a mission that has guards.
Help justify my early, not entirely wise choice of game name by holding someone at gunpoint with the Resolver.
Conceal your presence at the DataSec break-in from Mayfield.
Use the Hushcracker to jump through a window silently (outside of the test lab).
Wire an elevator button to trigger something when the elevator arrives.
Voluntarily tell Katie the truth.
Use the Dropshot to land silently from a great height.
Knock a guard out by opening a door into him.
Use the Crosslink to create an infinite loop that burns itself out.
Leave no living witnesses to your presence on a mission that has guards.
This is an achievement in name only. No-one admires you for punching a guy that many times.