I personally wouldn't want the IG. Too much raw power. I honestly wouldn't want the responsibility. I'd much rather have a more personal-based item, like
I guess I'd have to go with the Mandarin's rings, even though I'm not a huge fan. But in terms of an item, those would be the most fun for me.
A lot of the others have serious downsides. The Gem of Cyttorak would be great, but if it insists on me being a bad guy (spreading chaos) to really use it, no thanks. And the IM armor--I just don't feel that up on technology.
And being the myth fan that I am, I'd love to have Mjolnir...but I couldn't lift it, so what would be the point?