Name a song where the bass guitar is the lead instrument?

Pretty much anything by Primus

Soul to Squeeze by the Chili Peppers. It's awesome.

Another One Bite the Dust by Queen
Under Pressure by Queen & David Bowie

Anesthesia (Pulling Teeth) by Metallica
Orion by Metallica

not to many

Anything by Primus. Check out anything by Victor Wooten....he did an album with 6 string fretless player Steve Bailey- 2 bass players and a drummer! KILLER! Charlie Hunter plays a seven string bass/guitar, when you listen to this act relize he is doing the bass and guitar at the same time! He is not human. Stu Hamm has some great all bass stuff too. Really check this stuff out, its not only bass up front it rocks. Almost didn't mention Jaco Pastorious....
See if you can find an LA cat named Marco Mendosa (his version of Teen Town......SIK ......youtube)!

"School Days" by Stanley Clarke (The guitar takes the lead part of the time, but the bass gets the longer solo)

"Birdland" by Weather Report (Jaco Pastorius played most of the melody)

"Regret" by New Order (There are two bass tracks and one plays a lead role)

"Another Man's Woman" by Atlanta Rhythm Section features a long bass solo.

Anything by Wayman Tisdale features the bass, sometimes two or more bass tracks.

"send me your money" - suicidal tendancies

and I think "Iron Fist" - Motorhead, verification???

Edit 12/12 - forgot 1 - "Peace Sells" - Megadeath

"Another One Bite The Dust" by Queen