HALO 2!!! It has to be, i am surprised that not more people have said the same, but each to their own. I pick H2 because of everything about it, the campaign, the online multiplayer, the rank emblems how they got from different colour box colours to the shooting star and the moons to the level 50 halo! and super bouncing, the maps, the weapons, how you could move around and control the master chief in the movement, the double shots, BXR, BRB, firing 20 sniper bullets without reloading, or a 108 rounds of BR without reload and the overall gameplay and skill it took to play this game and reach high levels. Alot has changed throughout the years, I only prey that Halo 4 will bring back some of these things for me, as I personally hate ODST and Reach as they take no skill, and anyone can open up a can of whoop ass with ease, which may be good for some, but takes away all skill of the game i know and love. Long live Halo 2!