VLC http://www.videolan.org
plays: avi, mpeg, qicktime, vob, dat, divx
special: plays damaged avi files, u dont need codecs installed
cant play: real media formats
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alibi
__________________
What I've felt, What I've known; Never shined through in what I've shown
Never free, Never me; So I dub thee unforgiven
-Metallica
Just to add to alib_i's post, it also plays weird formats such as .mkv (Matroska) so it is a good option if you want to play lots of different formats with a single player and without having to install tons of codecs