My favorite would have to be that of the LF3XT. It offers the best of both simple and fully programmable. You can have any level from very low to full power, variable strobe or beacon, or SOS come on at first click. From any setting high is only a press away. In the simple user interface the light is rampable, has last level memory, and low or high are just a click-press or double click away. And then there's the other features like battery voltage report, overdischarge protection, momentary, etc. Also, the electronic switch functions smoothly and silently. Very difficult for me to find fault.
My least favorite is probably the multilevel twistie setup like the L0D, though it works fine and I very much like the light.
I suppose if I was to design my own it would work like the LF3XT, except through a side clickie, similar to the Proton Pro.
Geoff