Literally the first "mp3 player" that came up on amazon.
http://www.amazon.com/gp/product/B00...d_i=1264866011
It supports:
1. .AA (audible)
2. FLAC
3. MP3
4. Ogg Vorbis
5. WAV
6. WMA
7. WMA (secure)
If you have devices that only support mp3, then you have odd/old devices. It certainly doesn't represent the majority of devices out there.