Momentum is such an interesting and awesome concept I simply couldn't put it as anything other than first. I think I really great Pokemon could come about from this concept.
Save stall is interesting, since I definitely want a more defensive/balanced metagame than what we have now. I just hope that it doesn't create another incredibly CAPable (B-da-CHA!) defensive Pokemon, seeing as how hard it was to break CAP stall last gen.
And Weaponless is another very interesting idea with a lot of potential and many different directions it could go in. I'd like to see it.
Love all of these ideas, but the stall idea seems the best. Stall faces so many problems that even the best stall teams have gaping holes. Pokémon like Burunkeru help and hurt you at the same time (good spin blocker and special rain check, but it's defenses seem like they should be switched for it to perform much better) , and I would love to see stall still be able to work.
Momentum: It would be interesting to define the concept. Save Stall!: A good concept, even if I get the feeling from the start that this is going to be a Dark/Ghost (to counter Reuniclus) with the special defense to sponge Draco Meteors and Levitate... "Leading" the new generation!: Interesting concept.