1. Triple-H
A feud between Triple-H and Bray Wyatt is one feud which every WWE fan is waiting for. Though the two had a stare down on Raw when Wyatt did the dirty work for Triple-H by beating Roman Reigns, nothing emerged from that tease.
However, this feud can be a potential SummerSlam headliner. Triple-H could come back to aid his wife Stephanie to take control of Raw and could try to take out Shane, but, a returning Bray could come out and stop Triple-H. Bray could justify his actions by stating his desire to end the reign of Stephanie and Triple-H and becoming the harbinger of the new era.
With both Triple-H and Bray Wyatt both being intense and cerebral wrestlers, it would make a splendid feud where Wyatt can benefit from the heat that Triple-H generates from the crowd and become a completely face character.
At this point of his career Bray needs a solid feud to bring him back to relevance and give him the push he deserves. Maybe, a championship belt as well. But, if booked correctly his character would not require any championship to go over.