(I may have figured out some of these, but haven't written them down yet):

Flying by the Beatles
part of the theme from Rocky
Hazy Shade of Winter
Wah-Wah
Danny Boy (surprisingly easy)
part of the A-Team theme
Play That Funky Music
one of the Looney Toons themes
Something
There's a Place
Sunshine, Lollipops and Rainbows
O Come All Ye Faithful
The original Battlestar Galactica theme
The First Noel

Songs or riffs I have figured out how to play on the guitar:

Here Comes the Bride
What Is Life (2 of the parts)
Norwegian Wood (This Bird Has Flown)
My Bonnie
In a Gadda Da Vita
Happy Birthday to You
Every Little Thing
Auld Lang Syne
While My Guitar Gently Weeps
Another One Bites the Dust
Teacher, by Jethro Tull
The Futurama theme
part of the Star Wars main theme
part of the Darth Vader theme
that bit from Close Encounters of the Third Kind
Smoke on the Water
Do You Feel Like I Do
Day Tripper
Sunshine of Your Love
The Daily Show intro
The Colbert Report intro
Frere Jacques