Mannequin. It's one of my favourite Britney tracks overall, I really wish it got a release!

Freakshow, Toy Solider, Get Naked (I Got A Plan), He About To Lose Me, Drop Dead (Beautiful), Trip To Your Heart, Seal it With A Kiss & The AMAZING Ooh Ooh Baby

Roughly in Order:

Trouble for Me, Trip to Your Heart, Lace and Leather, Can't Make You Love Me, Heaven On Earth, Scary, Anticipating, What U See (Is What U Get), Selfish, I Will be There, Cinderella, Amnesia, Kill the Lights, Hot as Ice, Where Are You Now, Gasoline, Out From Under, Shattered Glass, Ooh Ooh Baby, Deep in My Heart, Shadow, I Got That (Boom Boom), How I Roll, When Eyes Say It, I Will Still Love You

Everything from Blackout pretty much, especially Get Naked (which I am sure everyone hated at first), Freakshow, Perfect Lover and Toy Soldier.

And Lonely from her Britney album.

Amnesia
Quicksand
Toy Soldier
Heaven On Earth
Before The Goodbye
What U See Is What U Get
Autumn Goodbye-though not an album track its one of me fave Britney tracks

I love that song! I wonder what the music video would have been like?