This deal is from the semifinals of the 2009 Spingold and caused me great embarrassment:
I was West and observed this strange auction: 

West north east south Larry       -- Pass Pass 1 Pass 2* 3 4 5 5 Pass 5 Pass 6 (All Pass)   * Drury

Vul: None Dir: North J 5 4 3 2 A 10 5 3 A 5 4 2   -- K J 8 4 Q J 10 9 8 J 10 6 4   7 6 Q 9 7 3 2 K Q 9 8 5 3   A K Q 10 9 8 6 2 K 7 6 A 7

I was on lead, staring at that five-card straight flush in diamonds. If the man above didn't want me to lead diamonds, he wouldn't have dealt me such an attractive holding. Could I possibly eschew (the fancy bridge term for "reject") the Q lead? My partner had bid clubs. Maybe I should lead his suit?

In fact I did lead a club, which seems harmless on the surface. But, watch what happened. Declarer seems to be off a heart and a diamond trick, but this is not the case. Declarer won the club lead, drew trump and ducked a heart. Finito! Can you see what is going to happen? Declarer was able to win my (belated) diamond switch in hand, cash the A, run trumps and squeeze me in the red suits. Try it.

With the hearts (remember--declarer had ducked one, won one, and ruffed one) being guarded only by me (West), I had to keep a heart in the ending. That meant I had to abandon diamonds and dummy's 5 took the 12th trick; -980.

Amazingly, the lead was the same at the other table, and my teammate also executed the squeeze for a pushed board. However, a diamond lead defeats the slam. When the defense gets in with the heart, another diamond is played. This breaks up the entries for the squeeze (again, if you don't see it, you have to lay out the cards and try it). Squeeze aficianados will realize that the standard defense to such a squeeze is to take out the entries.

Next time they deal me QJ1098, I will view it as a sign from above to lead the suit.