Well I've got one that trumps anything so far, although doubling on a hard 15 is pretty awesomely hilarious.
I was playing a $10 face-down DD game and some guy and his wife? girlfriend? mistress? not sure came in and sat down, and she had never played blackjack before in her life, obviously. She was having a hell of a time with the face-down signals (scratch the felt, tuck the cards, etc.) and the dealer kept having to tell her what to do, and she wouldn't do it, and the dealer would have to tell her again, and eventually actually demonstrate with this idiot woman's cards what to do.
Anyway the best came when the woman takes a hit, gets a face card (I think) and then tucks her cards (amazing she figured out these actions). When the dealer comes around and reveals all the hole cards after resolving her hard, she reveals this woman had an ace...and a face card in her hand. Yep, she took a hit on a blackjack.
She won the hand with a total of 21 but was only paid even money, of course.
I was covering my action at a table full of college guys last weekend
and saw all of the following moves in the course of the night.
Hitting hard 17 vs. 8
Standing on 14 vs. 9
Doubling on 5-3 vs. J
Splitting 4-4 vs. 7
Splitting 9-9 vs. A
(i) Hitting hard 17 vs. 8 ...
(v) Splitting 9-9 vs. A
Actually while these look bad plays, on rare occasions it can be correct to hit a hard 17 vs 8 and I'm told in the US if the count is high it's worth splitting 9s vs A. I see standing on 14 all the time in the UK - I think it must be based on pontoon or a basic desire to stay in the game.