so, I supose this might not be an exploit, but more "clever use of game mechanics" or just "very bad behavior", but it can come in pretty handy!
You know you can not kick anyone for the first 15 minutes of a dungeon, and you can also not kick more then 1 (?) player per instance run. There is an easy way around this though!
First make sure the vote kick will go through, either have friends in the party or make sure you have a good reason to kick.
Secondly, tell the person you want to kick to please relog his character for any reason, example: he is invisible to you, you cant heal him / your addon is ****ing up because of him or any other that you can think of.
When he goes offline, votekick him. You can votekick an offline player at any time during an instance or any amount of times!
Enjoy beeing an evil bastard.