Simply Abigail, "Double Rainbow Song"
The Gregory Brothers inspire a lot of folky bedroom singer-songwriter-style cover versions, but something about Abigail's plaintive wail as she powers through the group's hippie-inspired "Double Rainbow Song" elevated her on to the list. (Also, she's not horrible to look at, always a plus for the solo YouTube musician.)
Mike Penny, "Bed Intruder"
Mike Penny has played a series of Gregory Brothers covers on a Japanese instrument known as the shamisen. (His specific style of play is known as Tsugaru Shamisen, named for the area in Northern Japan where it originated.) Here's his unique take on Antoine Dodson and "Bed Intruder":
Roomie, "I'm Not a Witch"
Having to go on television and assure voters that you are not, in fact, a practicing witch seems to be a pretty solid sign your political campaign isn't going well. Yet that's exactly what Delaware Senatorial candidate Christine O'Donnell had to do in 2010 after footage surfaced of her on "Real Time with Bill Maher" admitting that she had "dabbled in witchcraft." (To be fair, she says she never joined a coven!)
The Gregory's turned O'Donnell's bizarre ad into a soaring ballad. Swedish power pop band Roomie (frequent coverers of the Brothers Gregory) pick up the tempo, and include scenes from viral sensation "Where the hell is Matt?" for good measure:
Walk Off the Earth, "Sunny D and Rum"
The Gregory Brothers version of "Sunny D and Rum" is one of their more claustrophobic, downbeat melodies. It's the slowcore of auto-tuned non-singing. Walk Off the Earth's cover re-imagines the simple tune with a funky bassline and manic energy. (Yeah, granted, they seem to find themselves pretty entertaining...but hey, it's a good cover):