I'm still using a samsung z5 I've never really wanted to change it although I don't think it's sold anymore what I still like about it is the battery life is around 28 hours and it can play OGG files. No doubt sooner or later the battery will die on it though then I think I'll go for another samsung or maybe a cowon.
Oh another big plus for it is you can just drag and drop the files on it no stupid software involved and it works on linux as well.
If I buy another one I want it to do the same I think cowon players are probably the best all round if I had to