As in portable player?

I suspect most people would most likely vouch for whichever ones they have used / use. So you will most likely get some biased responses.

Perhaps wise to google up on feedback about particular players. Find out what issues some users have with them. How good the product support is. How well the player is supported with 3rd party programs. How easy it is to use. How limiting it is also! (eg: which file formats does it support & which not supported & which ones with limited support. etc. Limits can be read in many ways.)