In this talk, we will introduce a new data structure, mutable.ArrayDeque, that outperforms most current mutable Scala collections like Lists, Buffers, Stacks and Queues. We will also go over implementation details needed for this to be part of the new Scala 2.13 collections library. We will then encourage the audience to contribute other useful data structures like Ropes, Zippers, Disjoint Sets etc. to Scala.