Btcd
This page is a stub. Help by expanding it. btcd is a full-node implementation in Google Go by Conformal. Its project page on GitHub says:
"It currently properly downloads, validates, and serves the block chain using the exact rules (including bugs) for block acceptance as the reference implementation (bitcoind). [...] btcd does NOT include wallet functionality and this was a very intentional design decision."
See also the btcd tag on Conformal's blog, especially the "ready for public testing" announcement.
Because BTCD uses an alternative consensus implementation, it is vulnerable to breaking consensus and fake confirmation attacks.