Techivation T-De-Esser PRO by horriblemind
It's a nice little plugin, it has all you need from a de-esser and offers some extra features on top of that (in Pro version).
You can manually select the desired frequency range, then set intensity, sharpness, attack and release controls to taste and even saturate the entire signal a little so it sounds smoother. I'm not sure there's any other de-esser out there with a saturation option. Personally, I wouldn't use saturation inside a de-esser, as there are dedicated saturation or channel strip plugins out there, but nevertheless it adds to this plugin functionality.
There's a lookahead option as well, for more precise control. Oversampling is a great advantage when you want to avoid aliasing artifacts from heavy processing.
GUI-wise, I think the processing knob (which controls the threshold) is a bit too large in comparison with other switches, making them very small in comparison. Perhaps those precise controls at the bottom of the plugin do not have to be seen all the time and could be in a drop-down menu or something, but overall, it’s a decent looking GUI.
I think this plugin could be just a bit cheaper though, as it is not a full-fledged channel strip yet.