#1 Brock Lesnar

This is the big one. There's almost no way the WWE Champion Brock Lesnar gets to enter the Royal Rumble at number one and then win the whole thing, as it's almost too crazy to think about. If Lesnar wins the whole thing, he probably gets to pick his opponent. What's to stop him from picking Curt Hawkins and win at WrestleMania in 10 seconds?
The absurdity of it all notwithstanding, this whole thing about Lesnar entering at #1 seems like a convenient plot device more than anything. It's a really easy way to determine who will challenge for the WWE Championship. Some poor shmuck just has to knock Lesnar over the top rope, he doesn't even have to win - Brock will probably be angry enough that a match could be arranged.
All that tomfoolery frees up the Rumble winner to maybe challenge the Fiend at WrestleMania. But that's a topic for another time (although I think we all know who's facing the Fiend at WrestleMania).