Halo 1, by far.
I can't stand Halo 2 and 3 online(not even referring to glitching, just the online multiplayer in general). not sure why, the game just does not transfer well in an online setting to me. didn't care a whole lot for the campaigns in both them as well. Loved the Halo 1 campaign and the LAN multiplayer was probably the best FPS multiplayer time I've ever had. 4 xboxes with 4 people on each in an 8v8 CTF match was awesome. my parents hated those all-day Saturday LAN parties we had at my house.

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