Crimson Tide (IMDB Link)

Plot Outline: On a US nuclear missile sub, a young first officer stages a mutiny to prevent his trigger happy captain from launching his missiles before confirming his orders to do so.

This is one of my all time favs... its really gripping throughout and even when it comes to the climax you know what the options are that it could be happening but you still are at the edge of your seats. Make sure you watch this.