I think "plumón" might be understood only in Mexico. The slender kind used to be called "plumín", but I don't hear that much anymore.
"Rotulador" is the most common name in the packages, but I have hardly heard anyone call them that. "Marcador" is the word I hear the most, for the ones with a chisel tip, and "plumón" for the fine tip. Yet, I think I've heard people call all Sharpies "marcadores" too.
There is also "marcatextos" for a highlighter, but in the package you will often read "resaltador".
