My favorite scene in "Alien" was the Nostromo landing sequence. I've seen lots of scenes of spacecraft landings in movies, but the nostromo's landing was the most believable. I really had the feeling a professional crew was struggling to land a truly massive vessel on a planet, fighting wind turbulence, unfamiliar terrain, a storm, etc and the ship was likely made with atmospheric operations as a secondary consideration. (I've taken dumps that were more aerodynamic than the Nostromo was.) Dated graphics and quaint technology asides this scene really holds up and gave me a more in depth sense of landing a huge ship on a planet than any landing scene in voyager, for example, ever did.
Let's see . . . I love the St. Crispin's day speech in Kenneth Branagh's HENRY V.
It literally makes the hair on the back of my neck stand up.
The courtroom scene between Joe Pesci and his girlfriend in MY COUSIN VINNY.
And the concert scene near the end of O BROTHER WHERE ART THOU?
Just to name a few.
most of the training scenes in 36th Chamber of Shaolin, but especially the one where he works out how to get across the logs to the dining hall.