The mens "town shirts" and the crystal. I like the shirts, but now that they are $500-$700+ each, I really try to hold off until the sales, as putting up with the ink smudge on the H tag is more than mitigated by the $300-$400 savings! And the crystal, while beautiful, is priced at a level I just cannot justify paying retail for. My dream is to arrive at the BH sale with a full collection in the Tommy pattern sitting on a utility shelf marked down 70%. It'd still be a bit too expensive, but I'd sure not pass it up.
Other than that, the only things I buy at sales that I'd never buy at regular price at the stores are beach towels. I've bought ties on sale there that I merely liked and didn't love, and they've never been worn, so yeah, as others have said here before, whether it's on sale or retail price, if you don't love it, it's probably best to leave it for someone who will.