In a training exercise gone wrong back in 1989, Capt. Brian Udell had to eject at from his F-15 travelling at supersonic speeds. The force of the air on his body was so strong that it nearly killed him. Here is Udell explaining what happened.
The wind tore his helmet off, broke every blood vessel in his head and face, dislocated his left elbow so that it was pointed backwards and snapped both of his legs in half. His lips were so swollen that they "fit into the first three fingers of [his] hand."
His weapons officer had ejected with him, but only Udell survived what remains the highest speed ejection from a U.S. fighter aircraft.
(Hat tip to: WOT!)