gem of infinite suns, perhaps. ridiculously powerful little trinket, seems like it can be deployed in a variety of ways, it'd look rather BA when used, AND apparently it can undo the effects of the cask of eternal winter without hurting anybody or anything. thor was melting the coldest of ices right off people and buildings with this thing, and nobody got so much as a sunburn.
just seems useful, from a superheroic standpoint.
that, or a power ring. i simply wouldn't have the imagination to use it interestingly. "oh look, a ten-times scale-model bikini-clad supermodel just put out a fire, and is now attending to that one guy with no pants on." that guy is me, you jealous little peons.
Cosmic: pretty hard to top the 'gog, except you need all of it, if you're missing a piece, you're ****ed. ALE means you have to fight the Source.
I'll go with Astro-Harness. It's uber badass, and you basically get most of Orion's powers from having, even part of the strength and durability (amping!).
That or Barry Allen's flash costume......hey, it worked for Bart.
More terrestially, the Azrael armor.