Grinding The Orange Box for old achievements. Just played TF2 for the first time ever to see whether it's worth getting into that to pick some up. I may give it a go, to pick up some of the easier ones. Also playing HL2, which is still absolutely brilliant. It's very effective in being cinematic, with its set pieces and its music.
I got the "Zombie Chopper" achievement last night for playing through Ravenholm with only the gravity gun. Even just on easy that was quite unnerving at times.