Triangle grip
From Acrobalance
This is a very strong grip for use with opposite hands. To get into this grip have one person place their thumb between the first and second fingers of the other person then, palm to palm, have them grab onto the rest of their hand. The other person should grab the wrist of the first person with their thumb and first finger and grab the rest of their hand with the remaining fingers.
Pros and Cons
This grip is very strong and allows the each person's wrist to move. On the down side this grip is asymmetrical which makes it harder to learn. It takes some setup time to get into this grip and, in the case of trapeze or similar arts, it can't be caught into.