I know it's the basic tank but i really do love pld, it was my original class i started on and i still love it today. It's magic is super fun to use and i always feel so powerful playing it.
Ast would be a close second, i know it gets a lot of hate, but i think it's quote on quote 'terribleness' (even though if you know how to play it it's just as effective as the other two) makes it more fun than whm or sch.
Im not as big of a dps fan, but i still do enjoy playing my dnc a lot too, it feels satisfying to get off all those dances for big aoe damage.

Obviously these 3 are my main classes, but i picked them as my mains for a reason; i just really like them.