OKAY...
For Sabbath.. well.. any of the old classic stuff Paranoid, NIB, Sweet Leaf.. etc etc... if you wann f-em up, put the Iron Man version cover done by "The Cardigans"
For Iron Maiden, number of the beast, anything from the Piece of Mind album.
Rush - well so many... anything from the Moving Pictures, Signals, Power Windows, albums. 2112 (yes the whole thing).
It's obvious your friend is a big bass playing fiend since he is gravitating towards metal/rock bands where the bass players have lots of chops.
That aside put this stuff on as well for NEW
Determined - Mudvayne
Anything from Soilwork (Natural Born Chaos, Predator's Portrait, Stabbing the Drama)
Anything from In Flames (Reroute to Remain, Clayman, Colony, etc..)
Meshuggah - chaosphere!!!
OPETH - "Funeral Portrait" (I am not a big fan of the band but this song is FRIGGIN awesome, can't deny it's genius along with a few others)
I could write more on this but man I wanna leave work soon