MANDROP all the way to the bank.
Jax and Rammus are definently up there, Jax because of how often you usually have to 1v1 someone and rammus because of how fast he can get around.
Champs that have built in mobility and can move around the map quickly are the best.
The fact that every answer to the OP question has been different should tell you something.
Rammus, Teemo, Zil, Yi, nidalee, kayle, TF, Janna
Kat, Jax and Lee Sin can use their abilities to be fast next to someone.
Basically, if you're fast enough, you win.
In my opinion, tanky DPS characters really dominate Dominion due to their sustainability and damage output, allowing them to defend and attack control points.
Twitch is great.
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