 If you liked
Shaman King
|
 ...then you might like
Owari no Seraph
|
Both series involves making contracts with ephemeral beings that possess/come sealed into small objects that turn into gigantic weapons. Story wise, there's nothing similar about them. But "Friendship and Teamwork" is a big focus on both.
There is no extermination in shaman king, but it involves fighting similarly powered enemies just like in Owari no Seraph.