We've done this thread before so here are my old picks:

"The Golden Boy"
"The Aztec Warrior"
"El Flaco Explosivo"
"El Finito"
"The Professor"
"The Greatest"
"El Maestro"

Some newer nicknames I like:

"Hispanic Causing Panic"
"Hayemaker"
"Viking Warrior"
"Cobra"
"Cochulito"