Multimedia » MPlayer :
MPlayer is a movie player for LINUX (runs on many other Unices, and non-x86 CPUs). It plays most MPEG, VOB, AVI, OGG/OGM, VIVO, ASF/WMA/WMV, QT/MOV/MP4, FLI, RM, NuppelVideo, YUV4MPEG, FILM, RoQ, PVA files, supported by many native, XAnim, and Win32 DLL codecs. You can watch VideoCD, SVCD, DVD, 3ivx, DivX 3/4/5 and even WMV movies, too (without the avifile library).
MPlayer can be run from a command line as well as with many different skins of the GUI frontend.