I find the Argentinian (Argentine?) accent quite lovely, that vocalized and breathy 'yo me llamo'.... Uruguayan Spanish has that lovely, Italianized accent also.
Hehehe, it's so pretty to me, it sounds elegant.
I am also partial to the Venezuelan accent as I learned Spanish in Caracas. They sound a bit out of breath when they speak Spanish and they drop their s's
I find Colombian and Peruvian Spanish quite clear and neutral.
Not crazy about the Cuban, Dominican or Puerto Rican accents, don't know why exactly, it's so fast and loud to my ear.