Surfer...unless Flash can generate new sperm at superspeed, yet not squirt them at superspeed, or can fire off one sperm at a time, and with perfect aim. I don't think he can.
Wait, I forgot: speedforce is becoming like power cosmic: it can do virtually anything.
Then again, Surfer could probably do this shokushu goukan style (PC = Plenty C*m).
...okay. Back to doing something worthwhile.