Led Zeppelin 
Led Zeppelin II 
Led Zeppelin IV 
Houses of the Holy 
Sorry, but Led Zeppelin II is by far the most influential album and the early model for heavy metal. It spent 7 consecutive weeks at #1 in the U.S. and is Certified 12X Platinum. Plus it's my favorite, followed closely by IV. Image: http://www.ledzeppelin.rockvalhalla.com/wp-content/uploads/2011/09/led-zeppelin-ii-songs.jpeg
I agree, it is painful, but ramble on we must.