Santana was slushied by Karofsky in the episode "A Night Of Neglect". Brittany, it seems, has never been slushied.
Besides Santana the following have been slushied:
Rachel was slushied by Puck in "Pilot", By Karofsky in "Hell-o".
Sam was slushied by Azimio and Karofsky in "Duets".
Mike was slushied by Karofsky in "A Very Glee Christmas".
Puck was slushied by Karofsky in "Mash-Up".
Tina was slushied by a football player in "A Very Glee Christmas".
Mercedes was slushied by Azimio in "Hell-O" and "A Very Glee Christmas".
Quinn was slushied by Azimio and the football team in "Mash-Up".
Finn was slushied by Karofsky and later Azimio and the football team in "Mash Up".
Kurt was slushied by himself in "Mash-Up" and Azimio in "Audition" and Karofsky in "Hell-O".
Will was slushied by New Directions in "Mash Up".
Artie was slushied by the football players in "The Sue Sylvester Shuffle".
Karofsky was slushied by Scott Cooper in "The Sue Sylvester Shuffle".
Azimio was slushied by a hockey player in "The Sue Sylvester Shuffle".
