I've got a really rough bootleg version of "Feel U Up" which has some really simple but funky bass playing on it. The "pulls" are almost, but not quite, out of tune, which to my mind is the best thing ever.

Apart from that, I'd vote for

Head
Alphabet St
If I Was Your Girlfriend


Non Prince:

Stroke - Mazerati

Fishnet - Morris Day

I Don't Believe You Heard Me - Mtume

A Love Bizarre - The live version where Prince and the Revolution join Shelia E on stage
[Edited 12/17/09 14:43pm]

From the top of my head:

Lets work (obviously..lol)
New Position
Play in the sunshine (its buried a lot, but oh so souple, almost McCartney-like)
Sign of the Times
Alphabet Street
Dolphin
Call my name