Number one is ball tip probes for sexing snakes - just got really sick of relying on other people who were wrong way too often - these are essential. Can't say that we have compared brands - we have the set that Scales Zoo sells - has been perfect - for everything from very small corns to boas.
Second number one item is our RayTek MiniTemp temperature gun - love it - immediate indication of temp on any surface any time anywhere. Even though we use it many times daily - for everything from brumation temps now that it is dropping down to -40 overnight to water temperature when we do changes of the fish tanks, the battery has lasted well over a year. Great tool.