BDAntiRansomware is a free tool which Bitdefender says can "protect against known and possible future versions of the CTB-Locker, Locky and TeslaCrypt crypto ransomware families".
The program requires installation, but by default displays no interface, and doesn't appear to consume any significant system resources.
We had no difficulties with false positives or anything else, but if you do run into problems, protection can be temporarily disabled. Or, of course, you could uninstall it entirely.
The program doesn't require that you have any other Bitdefender software installed, and we didn't notice any extra marketing payload (there's no registration required, browser pages didn't start opening at the Bitdefender site).
BDAntiRansomware is a lightweight tool which protects against several of the most common - and dangerous - ransomware threats. Could be useful as a second layer of protection alongside your existing security suite.