I actually don't particularly like Rain Dance as an opinion. Sure, it utterly destroys Rain Teams, and thats neat, however, I really dislike he instant disadvantage you get when you run into Hail / Sun and Sand. You can try and dress it up as you like, but the fact remains a smart opponent will see your 2-3 swift swimmers, realise you are running a Damp Rock Team, and keep their weather inducer alive just to screw with your strategy. Then you realise that these sort of teams pack Rain checks anyway, which also provide obstacles to you easily sweeping. Sure, a 100% win against 99% of most rain teams is really cool, but I hate the obvious weakness to other weather teams (which are common) which is really really hard to handle, without losing out of swift swimmers (making you less effective at trolling rain) or Rain Dance users (making it harder to get your rain up).
Gravity
O.k, most people who know me are aware that I am a massive Gravity fan. The fact that the CCAT has quite a few people supporting Gravity is a source of joy for me, but I want everyone to think rationally here. Gravity is a tough team-style to make, sure, it gives us options (Gravity + Spikes, Gravity + EQ spammers, Gravity + Dugtrio etc) and it can be very effective when used correctly (Its very good in BW2 with the new tutors), but I can say with 100% certainty that its a very difficult strategy to build a team around, so do bear this in mind. Don't get me wrong, its definitely possible, and I think we can do it, I am just aware that its very difficult (tho I know exactly what sort of thing a successful Gravity team needs in this metagame) and some people might struggle to contribute to the project. Just something to think about.