Okay. I tested a bit Gliscor in the past few days, and while searching for nice things to pass the Sub on, I found out that most of them are weak to hazards somewhat. Voclarona was my first thought (and it's indeed awesome behind a Sub), but the same apply to Cloyster, many Flying types (Nite, Mence above everything else), and even stuff like the previously listed Kyurem will benefit a lot from Rapid Spin (I settled for Volcarona in the end, but we can take different paths easily). I just added a Starmie without thinking too much since it's the standard spinner in about 99% of my teams that need Spin support; however I noticed that it was doing much more work than simply spinning. I'll explain this better later; let me present my suggestion:
Starmie @ Leftovers | Natural Cure
Timid | 252 HP / 24 Def / 8 SpA / 224 Spe
- Scald
- Psyshock
- Rapid Spin
- Recover
Bulky Starmie, despite the apparences, is, well, bulky. It resists everything that hits Gliscor for super effective damage, namely Water and Ice, while Gliscor can take most attacks that trouble Starmie with ease (see U-Turn, Crunch, and the likes). It also provides Rapid Spin support, and status absorbing prowess thanks to its awesome ability. Apart from these obvious things, Starmie synergizes with Gliscor in other ways; first of all, Scald's burn chance means that things like physically attacking walls (Ferrothorn in particolar, that loves to switch in on Starmie) will have a hard time breaking Gliscor's Sub, especially if it passes to a resistance, which is indeed awesome (it gives a free turn on top on a free switch for our threat); furthermore, the duo forms an incredibly flexible defensive-supportive core that enables us to pick basically whatever we like, since hazards are already handled, status can be absorbed by both with ease, there is no glaring type weakness whatsoever, and many otherwise dangerous threats are already checked (see Keldeo, Terrakion, Breloom (OHKO'd by Psyshock after very residual damage), Scizor, Gengar and so on. As a bonus, they're both quite fast, which doesn't hurt either. So, while it may not seem obvious, Starmie makes an excellent partner for Gliscor, giving valuable support and enabling us maximun freedom for the remaining picks, so it's my suggestion for our second pick of this CCAT.