The zest would probably be wonderful in a tart witbier or some other wheat ale. As for the fruit itself, citrus fruits don't usually ferment very well, resembling vomit more often than not after the yeast are done with them. You could try serving the beer with a fresh kumquat on the side or experiment with squeezing just a little bit of juice into the beer just before drinking.
The Fiesty(sic) Goat Brewery est. 2007 & Clusterfuggle Experimental Ales est. 2009
Primary: Saison, Berliner Weisse, sLambic I, sLambic II, IPA, 70/-
Secondary: Orange Blossom Mead, Flanders Red I
Kegged: Fat Man Porter w/ 1469, Fat Man Porter w/ 005, Centennial Falcon w/ Conan, Centennial Falcon w/ Denny's, Barrel-aged Fat Man Porter, Belgian Dark Strong, Dark Mild