#1 Brock Lesnar
Yes, I'm well-aware that Lesnar could be leaving after WrestleMania, but I'm not talking a few months and then resigning. He's had contract disputes before, but this time around, he might not come back.
He's done a lot this time around. Multiple Title runs, breaking The Undertaker's WrestleMania Streak and has had matches with the likes of Triple H and CM Punk. But its time for him to go.
Unless Lesnar decides he wants to wrestle full-time, which I highly doubt, then he should go and do something else. I'm sure UFC would bring him back as Lesnar is a major draw for the sport.
You can tell he doesn't really care as he no-showed RAW this past week. Now that could be legit or story, who knows. But it still shows that he makes appearances when he feels like it. Everyone else wrestles every week. He pretty much wrestles once a month or so.
The world champion should not be a part-timer, WWE should seriously learn that. Lesnar can even stay away permanent. He seriously made enough money that he could retire now.