It can be the end of a movement, an act in an opera, the final notes of a symphony, or anything that's an ending.
Some of my favorite ones are (in no particular order):
Mahler's DLVDE: the ending passage is some of the most gorgeous thing ever composed, and is also an emotionally adequate end of the movement and the entire piece. In fact, I like it much more than the end of Mahler's 9th. Speaking of Mahler's 9th, I've always interpreted the finale as dissolving into a dying breath of indifference, and it's kind of... unsatisfying, to me.
Shostakovich's 4th symphony: the coda worked really well due to its contrast with the massive chorale immediately before it. Also well for shadowed by the quiet codas of the previous 2 movements.
The end of Tristan und Isolde: that's where the Tristan chord is finally resolved, along with all the emotional, moral and philosophical struggles that persisted throughout the previous 4 hours of music.
Berg's Violin Concerto: the way the final notes recall the very beginning of the concerto is so beautiful.