I'm sorry if topic like this exists, but i've been so much raging about grinding same rhakghouls on Taris that my head is about to explode.
I'm just 34lvl atm and haven't done all planets yet but i shall start:
My favorite planet would be Tatooine, yes a desert zone. I usually find desert zones boring, but i found Tatooine extreme fun. Fun quests especially as imperial agent, world pvp at the dune sea. Skull trap "IT'S A TRAP!" (If you know the world boss, you know what i mean.)
My worst planet so far would be Taris. I understand the planet was obliterated, but still i don't like the scenery here at all. Also the fact i had to go to Doctor Lokin multiple times through same amount of Rhakghouls all the time, also had bonus quest which wasn't linked with quest but had to grind through freaking sewers of atleast 50 Rhakghouls... but after while of doing class quests i find out i gotta go again through that place urgh! Hate hate hate hate hate that zone and it's rhakghoul army!