Finished Halo 3: ODST a couple days ago. That was pretty fun. I loved the noir atmosphere to it all. Though I'm still miffed that I somehow missed the last one or two audio logs.
I was hoping to have finished all of the preceding games (sans Wars) before Halo 4 came out but it doesn't look like that's going to be happening. Reach barely arrived in the mail today. Ah well, will definitely be pulling an all-nighter tonight on 4.