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 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.