The best video player I found is VPLayer - which plays MKVs with AC3 audio. MXplayer and Dice Player, which I tried previously play the video but can't handle the sound if it isn't AAC audio.
Ghost Commander is good for LAN shares.
Star Chart if you're into astronomy. The NASA app (free) for updates on Curiosity etc.
Osmos HD is a nice little game, as is Great Little War Game (like Advance Wars for the gameboy, etc)
I also grabbed Riptide GP which is supposed to show off the Nexus 7's graphics.
Oh, and I'm enjoying Traffic Wonder too, which is a neat little piuzzle game involving traffic and routes and timings.