Successfully engage in co-op mode with yourself.

Spend 8 Sentinel Batteries in the Fortress of Doom in a single save slot

Blow a hole in Mars

Complete a Praetor Suit Perk category in a single save slot

Get 25 kills in deathmatch

Complete a level on Nightmare difficulty.

Find a secret area.

Use the power of air to your advantage.

Tell the others what you think.

...but let's be honest, it works the same.

Search for other lands.

Pick up a star.

Install at least one implant in each system and body part.