One so far (a company called Pex, the founder's HN handle is doh). Always looking for more. :)

We've also done a decent number of investments through accelerators that were not YC. That's somewhere between cold inbound, cold outbound, and warm intro.

At YC we do this all the time. Its our bread and butter :)

This is the real question, I would like to see VCs here commenting on investments they made that were not through their network.