A capella men's ensemble version of Lady Gaga's Bad Romance
EDIT: This has been great, everyone. Thanks to everyone for all the terrific links and for introducing me to a number of artists I wouldn't have heard of otherwise. Seriously, the online rabbit-holes have been thoroughly enjoyable--even it I stayed up a bit too late a number of times.
I actually know almost nothing about her, but I found this song on a music blog (maybe stereogum?) probably at least 15 years ago and I never get tired of it. I will have to look at some of her other work.