Well the buzz is on Heath Ledger's version but I still enjoy the Joker's played by Jack Nicholson and Mark Hamill or Kevin Michael Richardson...
Jack Nicholson's Joker aka the Scary Uncle Joker... This version is not the goofy version from the 60's Batman series but more of the maniacal mass-murderer from the 1940's comics... Although Jack Nicholson's natural laugh is creepy enough, his age and lack of suitable physique brings his performance down... Also, Tim Burton's decision to make Joker the killer of Bruce Wayne's parents is not the best idea also... This version also wears a permanent grin due to an accident caused by Batman... Like Heath Ledger's version, This Joker's white face comprises of make-up not chemical mutation like the comics... This version also uses the trademark "Bang! Flag" guns from the comics but doesn't use the Joker gas... Jack's joker is NOT SKILLED IN PHYSICAL COMBAT and is easily defeated by Batman... In their final showdown, Joker's hand hurts when he punches the Bat in the gut...
Heath Ledger's Joker aka the PSYCHOPATH JOKER... The latest version of The Joker comprises of VERY VERY LAME jokes, psychotic laughs but no Joker gas or "bang flag gun"... His purple suit is also more sophisticated... Like Jack Nicholson's version, Heath Ledger's Joker also has a permanent grin but is due to the fact that he slit his mouth before the events of the movie... Like Nicholson, this Joker wears make-up but while Jack's Joker removes his make-up from time to time, Heath's Joker accepts make-up as part of his face and his face starts to show signs of infection as the movie progresses... In this movie, his crimes are somewhat more terrorsist-like which involves thousands of people... Unlike Jack Nicholson, this Joker is SKILLED IN COMBAT and uses his fists, metal poles and knives from his shoes to bring down Batman, he even punches and kicks Batman until he falls into a large net, giving the Bat very little chance...
Mark Hamill's Joker aka WACKY JOKER... The best animated Joker so far... He is still the usual mass murderer with trademark purple and green outfits, Bang flag guns, Joker gas and of course grenades hidden in giant Jack in the Box spring up toys... But, his profile is somewhat more wackier than other versions... Mark Hamill is also the actor who portrayed Jedi Knight Luke Skywalker in the early Star Wars movies by the way... The Joker from the first season is quite skilled in combat and is known to defeat the Phantasm, Mr Freeze and Scarecrow with a single punch... The one in the second season is more cunning but looks much more skinny... The one in the Justice League cartoons and Batman Beyond: Return of the Joker movie has great strength, hurling a bag full of rocks against Batman, injuring The Bat but has little skill in combat... Bu the resurrected version in "Batman Beyond: Return of the Joker" has more skill in combat than any other version as he is inside Robin's body... He uses Joker gas very very often and uses Bang! flag guns on several occasions...
Kevin Michael Richardson's Joker aka the Circus or Clown Joker... This version is somewhat similar to Mark Hamill's take but has unique monkey like abilities such as swinging around and hanging upside down... He is also more clown-like than the previous Jokers... This Joker uses the Joker gas very often just like Mark Hamill's version but does not use bang! flag guns...