This is a fan game, but I thought it's awesome enough to post it here, yeah?
So, it's a fighting game, mostly inspired by Smash Bros. but has inspirations from other fighting games. The cast of characters are mostly from video games, but there are also some from anime/manga and comics. You can see all the teaser trailers here. This page also has a FAQ which explains a few things.
This game seriously looks awesome, especially for a fan game. The 2D artistry is amazing. Personally, I can't wait for the demo to be released.
The Fire Emblem characters I found, and recognized, are Hector and Eliwood as far as I can remember.