tonymead60 has it right with "Norwegian Wood" - it's so beautiful, maybe a bit tricky to get just right with basic strumming... I like to play finger-style the most, (on an acoustic guitar, that is), so I'd recommend:
The Beatles - Blackbird
Eric Clapton - Tears in Heaven
Led Zeppelin - Stairway to Heaven (of course!)
Opeth - Benighted
- Patterns in the Ivy (Instrumental)
Pink Floyd - Is There Anybody Out There?
- Hey You
(of course, anything else by the great Floyd - whether finger-style or not!)
...and one of my absolute favourites, Jess Buckley's version of Leonard Cohen's moving classic "Hallelujah"
... just to name a few... If you want to get REALLY technical into some amazing acoustic-guitar work, check out what you can find of Antoine Dufour - he uses a lot of really cool tricks, on and off the fret-board, percussive stuff on the body of the guitar, etc... Check him out on YouTube if you haven't already been blown away by his stuff!