For a true tactical light, Acebeam L16 has a rear button that is turbo mode, every time, all the time, no matter what. The side button lets you access lower modes--click on, click off, hold down to cycle modes; it comes back on in the mode you left it in. Too big for a pants or shirt pocket, perfect for a holster.
For something that will be in a pocket, maybe a latest-generation Zebralight fits the bill. You can program them to come on at any level, and cycle through different mode groups if you want. For cycling, I have one programmed to come on at ~900 lumens, and switch to ~200 lumens with a double click. I made it a 2-mode light; but, you can make the modes whatever you want (I have another ZL set up as a 1-mode light for my wife, and others set up as 6-mode lights). For the OP's situation, I might program it to come on in "traffic stop" mode every single time, but access the highest mode on double click.