Metal Slug 3 (iTunes link; $7) is one of the major game releases of late, receiving very good or even raving reviews (that of Touch Arcade is HERE)
Having found out that the initial – rather high – price didn't get slashed after a month of the release, I've purchased the title today, only to find out the promised, external hardware game controller (iCade) support just didn't work.
A quick note: other, decent iCade-friendly titles