This was a hand from Division 2 of England's Premier League yesterday:
2♠ was a constructive weak 2 (about 8-11 HCP). 4N = RKCB(?), 5♦ = 1 or 4 key cards. 6♦ was not completely obvious, but intended as choice of slams and south eventually passed. Now west came up with a Lightner double requesting a ♥ lead - a particularly dubious choice given that he would actually have been on lead against 6♦! North decided 6♥ might be safer, and east doubled for his own reasons (perhaps he was confident ♦Q would be a trick).
West led ♠J, and south led a "low" ♥. When west carelessly played low himself, he found ♥5 wasn't so low after all when it won the trick! Note that ♥5 wasn't just led for effect. If declarer leads ♥10 west might realise that he ought to go up with ♥A! Now he can return a ♣. Declarer's only way back to hand to repeat the ♥ finesse is by overtaking ♠K. But now there is no way back to dummy to cash the winning ♦s after establishing the suit with the marked ruffing finesse...