The flashlight-laser is introduced in Ringworld as the ultimate multi-purpose tool.  At a wide aperture, it can be used as an efficient version of our current flashlight.  Yet as one increases its focus and intensity, its powers to illuminate can turn deadly as its green, pinpointed light cuts through most materials in a matter of seconds.

Throughout the Ringworld journey, the flashlight-laser is used by all characters in different ways. 

Nessus, the cowardly and non-violent “puppeteer” creature, carries the flashlight-laser as a useful tool which in dire need he can use as a weapon.  Speaker-to-animals, a savage and carnivorous “kzin” creature, uses the flashlight-laser mostly as an aggressive tool.  And Louis Wu, the old, curious human traveler, uses the flashlight laser as a tool of power, trying to impress the natives he finds in new worlds with its power.

Such a wide ranging tool could certainly be useful in our current circumstances on earth; although its power range would make it important to restrict its access.  You may be surprised to find that a similar tool is being used by police officers right now.