* NOT REALLY SPOILERS BUT JUST IN CASE SOMEONE GETS PISSY I GIVE AWAY SOME MINOR PLOT POINTS THEN HERE...SPOILER *
BEST: Twin Peaks - For a show that had to wrap up its story so quickly, it was so effective and the final 30 seconds still give me shivers to this day. One of the ultimate cliffhangers in TV, it ruined me (in a good way).
WORST: One Tree Hill - As soon as all the characters were adults and Chad Michael Murray left, this show was doomed. The finale was so infuriatingly frustrating, with no appearance from Lucas or Peyton, that cringe-worthy part where every character gets a monologue and "oh everything is so happy for everyone, it's going right for us all" really pissed me off. And the ending was like 10 years in the future and freaking character had aged! Come on make-up department, you can do better.
NOTABLE MENTIONS: Mash - Never watched the show but my Dad claims it's the best ending to a TV show ever.
HIMYM - The ending would have been SO much better if it wasn't rushed. They could of easily squeezed a tenth season. Good idea, but poorly executed.
Californication - With the main focus of the show being the "will they or won't they?" with Hank and Karen, I felt cheated when nothing had been resolved, in fact it just felt like a normal ending to a normal episode.