What did this poster write that got you all so down on him?
Actually, I would go with the flashiest looking one (with a decent sound, of course.) maybe with the biggest shockmount.
Rap music is very much about attitude and delivery --(yes, even the "intelligent" rap-- and everyone ought to make sure that thry aren't thinking about "rap that white people like" as the same thing as "intelligent rap...")-- so a mic that looks impressive really might be inspirational to the artist.
I'm not saying this to insult the intelligence of the artist or anything, but bling factor is a good thing. I've been seeing MXLs with gold tone matal on alse used around here for fifty bucks. (Fitty, in the vernacular) Just don't tell anyone what you paid.
And, I would guess, a good pop filter.
I don't have any experience recording rap vocals, but I imagine that a mic that responds pretty evenly from a range of distances would be important. A lot of rappers move around a lot to generate the rhythm and feel of their verses-- you don't want the bass of proximity effect going wildly up and down.