Halo 3 is my current target for completion.
Halo: Reach: Find the hidden binary signature. - Halo: The Master Chief Collection
After 9/25/08, complete Halo on 4-player Legendary LIVE co-op, with Iron, and everyone in Ghosts. - Halo 3
Gain at least 15 population from a single wave in a Reinforcement game. - Halo Wars