I have the Stylus green light from Streamlight[:-]. It is no bigger than a pen and has a good retention clip that has never failed me. I use it at work daily. It is very bright for its size and has a push button or twist on feature. It uses a 100,000 hour bulb and uses 3 AAAA batteries that come with it. I have used them at work for over a year and never had to change batteries.
In the woods it does a pretty good job but still has trouble picking up those small branches that seem to always find your face[:@].
I also have a headlamp from streamlight that is small and lights up the path much better but is more noticeable to others around too.

Good luck hunting this year.