Things I probably shouldn't have bought:
Bastion Press' Alchemy and Herbalism - I bought it cheap at GenCon but I haven't read through it more than once. It might be good if I were running a wilderness campaign, but the rules for making new substances are a little too specific. I think they could have been covered with other existing skills and feats.
Mongoose Publishing's Quintessential Fighters - Far too little substance and flavorless rules for me.
Things I'm Glad I Bought
I'm glad I bought almost everything else, but particularly Necromancer Games' Tome of Horrors, Malhavoc Press' Requiem for a God, When the Sky Falls, Book of Hallowed Might, and the Book of Eldritch Might I, II, and III, and WotC's Forgotten Realms products (all of them).