6. Dean Ambrose
It's easy to forget that Dean Ambrose was a dominant United States Champion (er, mostly because he never really defended the title while he was part of The Shield), and having him pursue it once again could work really well. After all, with Roman Reigns' feud with The Wyatt Family finally at an end, the Lunatic Fringe stepping out of his shadow and getting back on with his own solo career is something that's long overdue. As you may recall, these two had a cracking "Beat the Clock" match on Raw last year, and so the chemistry they share being stretched out into a feud between Ambrose and Del Rio has a ton of potential. Ambrose also stands out as something of an unexpected rival for Mexico's greatest export. Not only are their styles vastly different, but so too are their personalities, and that alone should be enough to ensure that we get a rivalry that's actually worth tuning into and getting excited over. Given that he's come so close to both the WWE World Heavyweight and Intercontinental Championships in recent years only to fall short, it also wouldn't be a bad thing to finally put some gold around Ambrose's waist, but obviously not if it comes at the expense of the returning Del Rio's momentum.