Think my No. 1 choice must be Eartha Kitt singing "Santa Baby". Apart from Bing Crosby, Dean Martin and Frank Sinatra everything else is bubblegum.
Brenda Lee deserves an honourable mention for "Rocking' around the Christmas Tree" though, if only for the immortal line "We'll eat some f***ing pie" (actually I think she sings "pumpkin pie" but it sounds for all the world like something else...!)