The team I had in my most recent go of X, a Wedlocke with no bag items in battle, was a pretty solid team.
Greninja + Klefki - Klefki came in after Lysandre's Mega Gyarados killed my Reuniclus. The Greninja was a great team member, had Modest nature and hit hard.
Medicham + Tentacruel - I had these two after Clemont beat my Fairy duo. They did extremely well throughout, against many trainers and even got things done against Diantha almost perfectly.
Lanturn + Durant - Durant was a late addition and only did a little bit against Wikstrom, but for Lanturn I used a Stockpile strategy, which was awesome against Siebold and really came to the rescue against Wikstrom's Aegislash and Scizor.
I also used (in the order of when they died) Pikachu, Diggersby, Florgés, Azumarill, Bibarel, Dodrio, Reuniclus, Hippowdon and Gourgeist. I was quite proud of my final team, even if I had a bit of a "reverse choke" at the end (read: losing some against the Elite Four then not losing anyone against the Champion).