SMPlayer is somewhere between the full-bodied Miro and the super-lightweight VLC Player on the video player spectrum. The freeware player, intended as a front-end for MPlayer, supports an impressive list of features and options.
The list of supported formats encompasses both major audio and video codecs and does a good job of trying to differentiate itself from the competition. One of the best features is that the player will remember your settings per video, so if you quit the app in the middle of playing, it'll restart it with the exact same settings as before. It can also handle a fairly comprehensive range of formats, including AVI, MKV, OGM, MPEG, VOB, 3GP, ASF, MOV, WMV, MP3, and OGG, as well as DVD playback and streaming audio and video from Internet sources. That's quite a list.
Subtitles are fully customizable, including color, font, and size, and the mouse wheel has been given some useful functionality: it can be used to search backwards and forwards in the video, and the center click toggles the mute control. The app also works on both Windows and Linux, and it's supported in more than 20 languages. There's also a karaoke filter that removes the voice track but keeps the music and subtitles.
The Playlist function was another useful feature that lesser players don't have, but might come at a price in larger ones. Being able to arrange a series of short clips and autorepeat them, as well as adjust the playback speed, swap icon sets, and tweak the aspect ratio make SMPlayer a lot more powerful than you would think after a cursory glance.
As you might expect, all these features add up to a hefty install file, at 17MB, and it takes up a fair bit of RAM. There was some sluggishness with tool tips, but the program itself suffered no stability issues. I'd recommend it as a strong secondary player or even a primary, if one of its more esoteric features is just what you need.