After a decade teaching high school physics, I'm still working on what order the material should come in. At this point I am pretty happy with the order for my regular-level course, where I start with momentum and collisions. Those classes will have their second test of the year later this week and after that we will use impulse to transition to our first mention of Newton's Laws and acceleration. I think it works really well in developing a strong student knowledge of a very important fundamental concept in physics: Conservation of Linear Momentum. It really bothers me that so many textbooks seem to just tuck that topic as an afterthought in a chapter somewhere after energy.
The course where I am really unhappy is AP Physics B. Perhaps it is only natural, since College Board themselves are unhappy with AP Physics B, so much so that they are splitting the course apart soon (some excellent details here). In training with VASS and NMSI I have been encouraged not to start with Mechanics, specifically to avoid introducing students to the physics course with some of the most complicated math and concepts (vectors and acceleration are traditional problem areas).
I have tried to start the year with Thermodynamics and Fluids before, and I think that went well. Most of the students remember their chemistry, so PV=nRT and some of the other topics actually make Thermo a good place to start. But there is a lot of hand-waving when talking about work, as in the work on or by a contained gas. And I admit I struggled to explain fluid physics to students who hadn't yet learned about kinematics, forces, or energy.
This year I started the AP course with geometric optics, and I think it went swimmingly. Reflection, refraction, lenses and mirrors are mathematically easy and conceptually clear. The lab equipment is uncomplicated. And to be honest, lenses and mirrors are fun. I should write a followup at some point about the fun we have with those labs.
What did not go well was the obvious followup chapter in waves, interference, and diffraction. Student learning was much weaker, the material less intuitive, the labs less clear and helpful. Student confidence was damaged and I don't want to repeat that next year. As this year's class moves on to kinematics, part of my thoughts will still be with how to better teach waves (in a very limited period of time) next year.