It could be too early to ask, but do you have any design drawings or ideas on the general layout? I figure a hammer is good for scoring a lot of hit points, but it's hard to deal damage that way from what I've seen. I think vertical spinners are the best overall, large diameter single sharp tooth with little wedges to lift a bot into the blade would be most effective. You would want the most blade tip speed for the allowed energy.
I found a bit of a confusing point on the rules page. It say spinners are limited to 200j of energy OR 21ft/s tip speed. Does that mean unlimited energy with a 21ft/s speed limit, or unlimited tip speed with a 200J energy limit? That would make sense.
Anyway, just for fun I threw together some rough ideas for a bot with a non high energy storing spinner. I figure the usual top and bottom arms for grabbing. For simplicity, the top arms can rotate up 120 degrees, the bottom arms can rotate down 120 degrees to lift or flip itself over. The top arms, if allowed, could have permanent magnets on the tips, strong enough (maybe with a sand paper coating) to help grip an opponent, but weak enough to be able to let go. A thin blade high power retractable angle grinder could be hidden in the front, so you can grab and cut deep. The arms and grinder could easily be moved by normal high torque standard size servos like what RC cars use. I guess it all comes down to fitting that durably into 30lbs. Of course you could have various attachments for the arms too.
A rough sketch attached
