I myself think the Ratel FPV camera is great and now Caddx have released a new camera that uses the same sensor (SONY STARVIS sensor), but now in a nano form factor (14x14mm). Another fun bonus is that the camera has a interchangeable shell that lets you mount it as a 19x19mm or 14x14mm camera. Other key features are super low latency (4ms) and a nice glass lens. The camera also weighs just 3.5g.
This is a companion discussion topic for the original entry at https://blog.unmanned.tech/caddx-kangaroo--f0-9f-a6-98-nano-fpv-camera/