Fuck Food's supposed to be the first single, right? I mean...that's the obvious choice.
When he first spoke of the idea, he indicated it may be a single as he talked of how it would only be called "Food" for the single version. However he has since talked about how it wouldn't be single material/radio friendly/etc. and people are giving him flack for putting "mainstream artists" on a song that can't be a single.
I think generally, the single(s) are the ones singled out in the pre-sale advertisement or other such write-ups for the album. "He's a Mental Giant" and "Worldwide Choppers" were the two mentioned for the pre-sale, however the former doesn't have a title that strikes me as a single and the latter... I think would be a bit of a nightmare to release as a single due in part to the legal troubles already. Plus, it's not always a good idea to release a single with 6 other guys on it, now if they cut it to just him, Buss, Twista & Yela, then it would probably be a front runner as a single due to the star power on it.
If history has shown anything though, the single will actually be a "solo" track. Aside from the "digital singles" (thus, I mean those they pushed to radio or those which they have done videos for), they've always been a solo cut (apart from someone like Krizz on it for hook duty and such).
A few weeks ago, they were talking about that Jessie J/B.O.B. track or whatever, "Price Tag" I think it's called, on the radio here. One of the hosts commented that "I'm going to call B.o.B. Midas from now on, because anything he touches turns to gold" so maybe they'll go with the B.o.B. feature, haha.
EDIT: Speaking of Cee-Lo, based solely on the feature alone, that might be a smart route for a single based on the success he's having.