I found this in a playground in Dallas when I was 7. It was mixed in with the gravel, which was polished "river rock" that I imagine had probably been dug from a quarry and run through an industrial rock tumbler. As a result, I have absolutely no idea where it originated. It's about 15mm long, feels smooth, and definitely isn't serrated.
I know an exact ID is pretty much impossible, but I'd like a general idea of what it might have come from, even if it's something as broad as "shark". It looks a bit like some of the teeth in a box of assorted fossil shark teeth (you know, the gift shop kind) that I have, so that's my current guess.
I can try to find a better camera if better pics would be helpful.