Just off the top of my head, I'll say The Stones "Satanic Majesty" cover with the real working Lenticular was cool, as was the Stones "Sticky Fingers" Warhol cover with the real zipper that caused a lot of problems in shipping;
Wish You Were here was great, obviously,
But this was over the top, even in the seventies. My dad 'bout had a heart attack when he happened to spy this one:
Steppenwolf, "For Ladies Only"