None, although I'm sort of a "black hole" for knives; I rarely let anything go, and only then if I have at least three more of the same model in reserve.

I do have regrets about knives that I didn't buy though. I was really on the fence about a couple of the Swamp Rats from last night's 'ganza. The hollow ground Rodent Solution was calling, but I kept reminding myself of two arguments:
1) The Swamp Rat store has CG Rodent Solutions for $108.95, so that satin/hollow ground option nearly doubled the price.
2) I already own several Mud Puppies, which I think fill the same niche, so it's hard to justify buying hg RSs.
I know that those arguments are just as true this morning as they were yesterday, but another piece of my mind is telling me I should have gone for it.

Similarly, there was a shiny version of the paratchute mandu, but I already have a couple of the originals, so why spend $198.95 each for something that is the same as what I already have, just prettier? The answer to that is because I'm going to feel like I should have when people start posting pictures of theirs.

I had serious buyer's regret over the Hammered Wardens from the '09 VetDayGanza. I ended up buying one through the BladeForums Exchange -- I liked it well enough that I still wish I'd gotten a few at retail. Oh well, you can only store so much, and if it doesn't spoil and you already have enough, then it's silly to keep buying more -- that doesn't keep me from wanting to though.