I would be surprised if it wasn't Spidey.
I have been enjoying NOW a lot, so i'm even excited for the inevitable A-listers.
Here's my wave guess:
Hulk and Ironman
Thor and Rogue
Spidey and Hawkeye
Wolverine and Captain Marvel
Also a SDCC boxed set of the FF (Antman, Medusa, She-Hulk, Ms. Thing) would be the bees knees.