I've been dabbling around with the combination of Heatran and Gliscor. Aside from its huge Water-type weakness, it has been doing quite well for me. Heatran is invaluable; its typing checks a huge amount of threats, such as Genesect. While Gliscor's typing takes on a lot of physical attackers, such as Terrakion. I had the idea for this core when someone on #othermetas said that "Genesect + Terrakion is strong". To address the Water-type weakness, I played around with two Pokemon - Rotom-W and Celebi. Rotom-W was mediocre, while it dealth with most Water-types, and provided an additional Ground-type resistance, it simply wasn't strong enough. I liked Celebi slightly better, its higher Speed meant that it could outspeed Genesect, not to mention Leaf Storm is pretty darn strong. The popularity of Heatran pretty much means it's forced to run Earth Power but that's fine.
I'm liking Protect so far as well; knowing what move your opponent will make in a tier that's so reliant on synergy is invaluable. I've ran it on Heatran and it's been nice for random HP Grounds or the like. Although I've since ran Air Balloon so it hasn't been needed as much.
I'm interested in trying a simple FWG core, or a Dark/Fighting/Ghost core.