This is one of the best “tiny” features I always miss in every application. Not sure which apps have it, but 3dsmax has it probably forever. This consists of two parts:
1.) Doing whatever action with LMB (moving object in viewport, moving a slider or spinner) is canceled if RMB is clicked (while still holding LMB). Right after RMB is clicked, any action is undone as If the action was never done. Also LMB behaves as if LMB was also released (object is no longer hold by LMB even if it’s still pressed).
2.) Rightclick on spinner/slider re-sets it to it’s default value (if there wouldn’t be default value (like for transformations), then to “0”). This is probably a bit duplicate functionality to the “reset to default” arrow that’s already in Rocket, but still the RMB to reset is much faster.