Theres actually a lot. Some people defend TDK plot holes as interpretations of "movie magic", while I just see it as an obvious WTF moment.
-I wonder why they call him The Joker?: Joker is just standing in broad daylight waiting around for his ride to get to the bank. The car stops before he even puts his mask on, yet, nobody in the car got a look at him, and is wondering who The Joker is.
-Its all part of the plan: It doesn't even come close to making sense, and his reasoning keeps getting distorted. Refer to this for a chuckle, and for seeing how The Joker's plan doesn't make sense. http://www.cracked.com/article_16848_p2.html
-The Joker is locked away at the end, but his plan shouldn't succeed: The entire ending just made me go WTF, that doesn't even make sense! Dent went crazy, and started shooting everybody. The Joker "transformed" him, so The Joker cant win, cause Dent is the shining hope for all of Gotham.....But what about The Joker knowing, and Maroni, or Rameriz, or the other cops that had a 50/50s chance at living, that probably did as well? So now the title of the movie "The Dark Knight" is a waist, cause Batman shouldn't be on the run, because people DO
know about Dent.
-Huh Rachel?: Why does Rachel ask how Dent is after her and Batman fell, when she clearly saw Bruce put him in the closet?
-Jokers bomb escape: How did the bomb kill everybody in the cop station, except for The Joker and Lau?
-The cops at the assassination attempt on the Mayor: You see a bunch
of cops giving a salute to the old commissioner, yet, when The Joker and his goon fire one shot at the mayor, ALL
of the cops that had guns drop them and run away scared.
-The mountain of money: Joker only kept half of the 68 million that Lau took. So you're telling me that a mountain that high and wide is 34 million dollars? Maybe
34 million in Ones, but thats still debatable in itself.
-Alibi: Wayne makes an alibi, by going on a cruise with all of the ballerinas. Ok, so they all decided to ditch out on their performance to go on a cruise? And Bruce only made an appearance, so its not to much of an alibi, also seeing as hes walking around Hong Kong in daylight
-I don't' want to kill you, what would I do without you: The Joker claims he doesn't want to kill Batman, cause he's "to much fun", and he also claims Batman completes him. Well, why was he trying to kill Batman at the beginning of the movie? Then, The Joker thinks Dent is Batman, and makes a plan to kill him in the SWAT truck, yet, minutes afterwords, Batman completes him?
-Holding cell: Who in their right mind leaves a psychotic killer in a holding cell with just one
guard, who happens to not have a gun.......inside the cell where the killer is?