Super Speed (like the Flash).
That, or the ability to cast charm monster at will.
Cheers, -- N
I think it's hard to beat the Martian Manhunter's shapeshifting. He can turn into giant monsters for combat, tiny insects for surveillance/hiding, and can impersonate specific people. The possibilities are pretty endless.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.