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