Okay, using the formula of first letter of first name, and first syllable of last name, my rap name would be J-Con. My forum handle would be O-Mo. Of those two, I think I'd rather hit the mic as J-Con.
Using this for the names of U.S. presidents, there have been some pretty good rap names.
Z-Tay (This one's my favorite. If there's ever a rap group where they wear costumes of dead presidents, I want to be Z-Tay)
If you take some liberties with Eisenhower, he could be D-Ice.