Well if we are talking about anyone here here is my list
1. Kelly C. and Adele
2. Kelly C. and Josh Groban..I know it sounds cheesy but i would die..
3. Lady Gaga and Britney..No words ppl..
4. Beyonce and Kelly C....I really want them to mashup Already Gone and Halo just to make fun of the whole issue
1. Beyonce and Mary J. Blige
2. Kelly Clarkson and P!nk
3. Taylor Swift & Ke$ha
4. Jennifer Hudson and Fantasia
5. Justin Timberlake and Usher
6. Beyonce and Christina Aguilera
7. Kelly Rowland and Usher
8. Brandy and Beyonce (a real collab, not just a mash-up of two demos)
There's no need more words for that, the world would just surrender to their feet and it would be the best collaboration ever so there wouldn't be necessary anymore collabs