I found a media player call "Wuzhenhua player" that plays more video format that other media player support from a Chinese android forum. I believe this is the first media player in android that support flv, rmvb, rm, and flac file format I have ever seen. The development is still in every early stage, so it's just a proof of concept for now. The app doesn't support full screen and auto rotate, but it DOES play flv and rm video as I have tested it from my Droid. It got potential to be the "CorePlayer" on android. That's why I think we can give it a try, and share this app.
Wuzhenhua player support format: 4xm,8bps,aac,ac3,eac3,amv,ape,dca,imc,alas,rm,rmvb ,nuv,ptx,tta,wma,wmv,flic,
P.S. I do not develop this app, all credit goes to the developer WUZHENHUA, and there's a source link from androidin.net