Iron Man from black sabbath is another pretty easy one to learn. Many sabbath songs are. If your into Korn, they have pretty simple songs to play as well, but they use 7 strings, of course that can be arranged for a six string too.
Shook me all night long, by ACDC is another easy one that everyone knows. Many acdc songs are very simple to learn and play.
Theres always Stairway to Heavon too, just dont play it in a music store (so Ive read) it annoys people. I shy away from playing any cover tunes in music shops actually. Any way, hope these few examples are helpful. You can usually find decent tabs for them around the net too.