OK, after a few minutes quiet contemplation, and using only tracks currently on the iPod (i.e. not choosing tracks from the infinite) I have just listened to the following:
If You Gotta Go, Go Now / Bob Dylan
(Sittin' On) The Dock Of The Bay / Otis Redding
Black Man Strain / The Abyssinians
Magic / Bruce Springsteen
Back Off Boogaloo / Ringo Starr

Ooh Wee by Mark Ronson or
Yellow Magic (Tong Poo) by Senor Coconut and his Orchestra

I Can't Get No Satisfaction?

or how about the Beautiful South's

You Keep It All In...

Brown Eyed Girl?

Also, don't forget the Zappa classic "Why Dones It Hurt When I Pee?"
Sample lyric?
"I got it from the toilet seat... it jumped right up and grabbed my meat!"

The Strain by The Bonzos. Full of rhythm, full of soul, full of scatalogical rock 'n' roll.

'Pushin' Too Hard' - The Seeds
'Chocolate Cake' - Crowded House

Anything by Bogshed!

Richard III by Supergrass
Float On by The Floaters

Big Log/Robert Plant
Piece Of Crap/Neil Young

Go Let It Out - Oasis
Sit Down - James
Burning Ring Of fire - Johnny Cash
Song 2 - Blur
Golden Brown - The Stranglers
Lets Not Shit Ourselves - Bright Eyes
Brick Shithouse - Placebo

Oh dear. This is not the sort of thing that one wants to be discussing, is it? However, I do have the definitive gem for all lavatorial lyric lovers. Listen to Screamin' Jay Hawkins and 'Constipation Blues'. It has a happy ending.

(and don't forget Ian Dury's 'Poo-Poo In The Prawn')

A comet appears - The Shins ( a quick dash)
A rush of blood to the head - Coldplay ( touchdown)
Asshole - Tom Petty (speaks for itself)
At the bottom of everything - Bright Eyes ( the end is near)
Behind closed doors - Bobby Womack (privacy is all)
Breach - Willard Grant Conspiracy ( for the difficult birth)
Powderfinger - Neil Young ( keeping those farmers sweet)

Boom, Boom, Out Go the Lights - Little Walter
Something in the Air - Thunderclap Newman
Depth Charge - Marc Bolan
Up Around The Bend - CCR

Anything by Lou Rawls

....that would speed things up - couldn't get out quick enough!! Leave time to listen to something good somewhere more pleasant!

Locked out - Crowded House (kept waiting)
Something might happen - Duke Special (constipation)
How Long - Ace (is it a personal best?)
Hospital Food - David Gray (that always works)
I close my eyes - Dusty Springfield (nearly there)
Let it slide - Keane (aahh..)
Going thruogh the motions - Aimee Mann (I don`t remember eating that)
Something inside so strong - Labi Siffre (wait, there`s more)
Between my legs - Rufus Wainwright (not bad for a 40 year old)
Waterfall - The Stone Roses (nearly finished now)
The hardest button to button - White Stripes (happens to us all)
Its the little things we do - The Zutons (look back with a little pride)

Ain`t that enough? Teenage Fanclub - That one just came to me as well. Oops.

Oasis - Sittin' Here In Silence (On My Own)

Oasis - Gas Panic