What are the best boats for one-design racing?

The categories a

1. Performance Dinghy

2. Small sailboat under 29 feet

3. Mid sized sailboat 30-39 feet

4. Yacht class 40-50 feet

5. One man catamaran

6. Two man catamaran

7. Under 40' crewed catamaran.

Rule: Must be production boats with more than 25 built for larger boats.
30' +
More than 50 must be built for smaller boats under 30'.

Bonus: Your pick for the hottest one-design class in the foreseeable
future.