1. 'Crazy in Love' by Beyonce feat. Jay-Z
2. 'Dilemma' by Kelly Rowland feat. Nelly
3. 'Umbrella' by Rihanna feat. Jay-Z

Honorable Mention(s):
Usher feat. Ludacris & Lil Jon - 'Yeah'
Lady Gaga feat. Colby O'Donis - 'Just Dance'
T.I. feat. Rihanna - 'Live Your Life'
Nelly Furtado feat. Timbaland - 'Promiscuous Girl'
JAY Z feat. Eminem - 'Renegade'
Eminem feat. Rihanna - 'Love the Way You Lie'
JAY Z feat. Alicia Keys - 'Empire State of Mind'
Christina Aguilera, Lil Kim, P!nk & Mya - 'Lady Marmalade'
Britney Spears feat. Madonna - 'Me Against the Music'
Justin Timberlake feat. Timbaland - 'SexyBack'

I have more, but I'm going to stop =)