CustomSteve

CustomSteve is a mod that allows users to substitute default Minecraft player model with industry-standard model, most notably 3D models used by MikuMikuDance (MMD).

Demo
Several demonstration pictures and videos are available right now. Here are links to part of them:
 * https://www.youtube.com/watch?v=rGltAWLIEJw (may be blocked due to legal reason)
 * https://www.youtube.com/watch?v=zcWAIsZ2PV0
 * https://www.youtube.com/watch?v=q8C4r_sOfYI

CustomBuki
CustomBuki, according to author's introduction, is a sub-mod of CustomSteve that provides a fully customizable weapon system with 3D model format and custom sound effect support. Buki in the mod name is the Japanese romaji for "weapons" or "arms". Currently this mod is still a work-in-progress, and only few videos are available so far, for example, a demo made by ici2cc, the main developer of CustomSteve mod.