Windows SSH client
PuTTY is the best open-source terminal emulator out there. Unless you're having issues with it, there's probably no reason to change. That said, I have met several network engineers who much prefer SecureCRT. It's main feature is session/connection management; when you're making a change that needs you logged in to 15 devices at the same time, having a good tab management system is a big advantage.
There is a comparison of SSH clients on Wikipedia