Well, if we're going angsty for Wilt, I think "Lose Yourself" by Eminem is appropriate for both Good Wilt Hunting and, to a lesser extent, Hiccy-Burps. Plus, the rap suits the atmosphere of Wilt's home town.
For Coco, I can't beleive noone's suggested "Crazy" by Gnarls Barklay.
For Mr H, the best I can do is "My way or the Highway" by Linkin Park.