Since there is no confirmation on what the achievements will be for the game, aside from the time being, let's create our own!
Here's some of mine:
"KEEP IT CLEAN - 10 GS: destroy all environmental objects within the city."
"Terminator - 50 GS: Never use a health pack"
"Ray Charles? - 50 GS: Never use the low-light mode, VISR"
-
10GS - Jackals in the courtyard - As Sgt. Johnson, take out 5 jackals in 30 seconds. (a qoute from St. Johnson from Halo 2) 10GS - Riot Control - You and your squad take out a patrol with only melee. 20GS - Recon - Pass all of the patrols with out taking any enemy out. 10GS - Useless Ape - Take out the leader of an enemy patrol with a plasma pistol. 40GS - Did you see that?! - Use the spartan laser to laser 3 Brutes...with one blast.