Alright, this might be lame, but I need something to do. Feel free to add on!
1. When Gandalf, Aragorn, Theoden, ect. arrive at Isengard, when Treebeard is talking, watch Theoden`s horse. It is, shall I say, "going to the bathroom!"
2. When Faramir and the Gondorian soldiers are leaving Minas Tirith (just before Pippin`s song) when the camera is zooming up to Faramir (the first shot of him in this scene) there`s a creepy old lady smiling to his left! These people are basically riding to there death, and the lady is smiling!
3. When Elrond comes and presents Anduril to Aragorn, lood around Theoden`s tent. It`s fancier than my house!
4. When Legolas is climbing up the Mumakil (Oliphant) dosen`t he look a bit large to you?
5. I could be wrong, but when Aragorn, Legolas, and Gimli are entering the Paths of the Dead, Aragorn appears to dissapear into the darkness. Watch closely and you`ll see that he is really turning a corner.
6. After taking the palantir (when Gandy is talking to him) Pippin is lying on the floor. Through his shirt you can see chest hair poking out! (Hobbits have chest hair?!)
7. You can`t really see this now, but in theaters, when they are all at the Black Gate, Sauron is whispering Aragorn`s name. When you see Aragorn, look behing him to his right. Legolas is leaning out of the screen, but in theaters you could see his face. His eyes were squinted and He looked like he was about to vomit!
8. Through-out the movie (and TTT) Theoden`s beard is always a greenish color. Grody!
That`s all I can think of for now, but I`ll probably have more later.