At a cost of 4 for unlimited thwarting, Cannonball offers pretty amazing value, and with Knowhere and Starhawk a wide variety of heroes can make use of him so I'm surprised to see that almost all the decks that use him on this site go with Angel.

I think Journeyman2 was the first to point out the way these three cards can work together (https://marvelcdb.com/decklist/view/32322/guardian-angel-1.0), and KakitaJamie was the first to use them in a non-Angel deck (https://marvelcdb.com/decklist/view/32647/adam-warlock-can-fly-1.0). I've been trying Thor (https://marvelcdb.com/decklist/view/34161/flying-green-thor-1.0) as Cannonball, Starhawk and Knowhere help a lot with Thor's weaknesses in thwarting and card draw, but really there are a lot of heroes who can make this work so I'm hoping to draw more attention to this little idea.