Stairway to Heaven
La Grange
Iron Man
Smoke on the Water
Paranoid
Inna Godda Da Vida
Strangle Hold
....All way excellent classics.....

My personal favs, though, are:
Black #1---Type O Negative
Summer Breeze (remake)--Type O Negative
Be My Druidess--Type O Negative
Angel--Astral Sleep
Reptile--Nine Inch Nails
Closer--Nine Inch Nails
Physical--Nine Inch Nails
and track #69 off of Undertow--Tool
Sober--Tool
Blue--A Perfect Circle
or just basically anything that Peter Steele, Trent Reznor, And Maynard James Keenan has done, or influenced