Yeah,flashlights on guns are a good idea. It turns out seeing what you are going to shoot before you do it is a good idea.
As far a rifle light there are a million options. You don't need it to fit in a holster,so it's whatever. Choose something with a clicky tail cap that is bright and move on.
For pistol lights go either Surefire(if you can afford it) or Streamlight and get a JM custom kydex holster.