Arguably the best media player for Mac and Windows also is available for Android and for iOS. It's the VLC Media Player, of course, and it can open and play virtually any file format -- including AVI, FLV, MP4, MP3, MKV, WMV, JPG, MPEG, MPG, RMVB, M4V, MOV, 3GP, TS, VOB -- without conversion or other annoying delays. It also plays DVDs and CDs, and VLC happens to be completely free and open-source. Anyone still using something else on Mac, Linux, Windows or any platform should download VLC and try it. A version for Windows Phone is in the works.