Free or Paid?
Paid, I recommend Sony Vegas Pro (I personally use it and very happy with it) while free tools such as VirtualDub can help in certain cases. It depends very much for the setup you're having, cameras and their formats, if you need to share the editing among several editors and so on.
DaVinci seems promising as a video editor (and it's free) but you do require a more powerful computer than you would with other software.