Timelost Protodrake
The Timelost Protodrake is a rare elite that flies around Stormpeaks. Many people farm him for the mount that he drops. The proto-drake has very few areas that he can spawn and wonder, he is usually killed shortly after he spawns as well. He has roughly a 6-12 hour spawn time and someone is usually looking for him at all times or knows when he will spawn. This makes his mount extra rare.
The hardest part of getting this mount from the Timelost Protodrake is trying to find him when he is up, before he is killed. He has roughly a 5 minute window from the time he spawns till the time he is killed. People want this mount for its unique look and also because it contributes towards the mount achievement. Of course, the lower pop your server the better chances you have of getting this mount.