The JETBeam Jet III M R5 has been one of my favorite tactical lights throughout its various incarnations. It is comfortable in the hand, has great design touches (two way clip, stainless steel bezel), and gives you the option of setting up the light how you want. When the head is tightened, you will always have max output. When the head is loosened, you can set the secondary mode to whatever you want. Usually this means a couple of outputs and maybe strobe. With the Jet III M, you have any output from min to max, strobe from 1-20 Hz, SOS, and a bunch of other flashing modes. The options are kind of ridiculous, so if you want a no frills, super simple light, this is not it. I personally like options and changing the secondary mode is simple enough that you can quickly do it once you get the hang of it.

For you zombie hunters, mounts and pressure switches are available. Here is a video that will give you a better idea of how the light works and performs: