The flight time is a good one. Asking about it before they book is one thing, but those who pull the trigger and book the way-too-early air and THEN come here to ask if they screwed up are the real champions.
I hate to sound like Andy Rooney and realize they are colloquialisms, but when you see it a few hundred times a year it tends to wear a person down. So here we go:
The "best" questions. "Which tour is best?" "Which ship is best?" "What port is the best?" "Which cruise line has the best food?" "Who has the best cabins?"
Close behind the above are those who I do not know, and have no idea what their preferences are, who ask questions along the lines of "which cruise line should I choose?" or "will I like Carnival?"