Personally I've enjoyed just about every role in the MMOs I've played. Tanking can get frustrating when boss aggro goes out of control and starts taking out your squishies, but I do like the "no f*cks given" playstyle when it comes to PvPing as a tank. My favorite role has to be heavy armor mages, even though your raw damage suffers because of the stat requirements for heavy armor, your crowd-control and disable durations are usually fixed numbers that only depend on skill level. An unkillable CC/debuff/disable machine is very, very scary.