Go buy something, wait a few days, then return it? I've done this more than once (under the philosophy of buy first, ask questions later; you can usually return an item but good luck finding the sale price again).
If you're looking for something to keep, do you cook a lot? Perhaps buy a nice chef's knife. I know we had a thread about that here recently.
Does it need to be tangible? If not, consider some sort of lessons; cooking, language, or musical (in the latter case you can also buy an instrument).
If you're feeling generous, buy a placard or brick of some sort for charity? My university sells bricks used in the alumni center, I reckon at least part of that goes to scholarships.
Going along this line of though, you could buy a present for someone. Do you have a significant other, family member, or friend who wants or would appreciate something? I have a friend who no doubt would love a box set of The Wire. Similarly, my father would love some accessories for his motorcycle. Heck, do you play multiplayer games? A few years ago a friend bought me a copy of tf2 so I could play with him. Later I bought a copy for another friend and gifted it to him on steam. You could do something similar.
Buy some tools? Or something like a jackstand, which may come in handy some day (more so if you actually work on your car, but then I reckon you'd already have one).
Buy some quality old school comic anthologies. I would get Calvin & Hobbes, but Peanuts would be great, or maybe Dilbert or whatnot depending on your taste.
That's about all I've got for now. Go ahead and shoot 'em all down