Neon Genesis Evangelion, DVD box set. I look back now and see what a stupid risk it was, because it was something like $200 back then(I don't remember the exact price) and at that point in my life the only anime I had really watched was DBZ and Gundam Wing + Endless Waltz.
Forever thankful I did that though, because I'm now a proud Otaku ;3
Still haven't purchased manga though. Was planning to go to Anime Expo 09 this year and pick up some manga/anime/etc, but I'm not sure if I'm going to be able to go (big problem is hotel room costs, and no one to split with).