Ring any bells? Maybe a children's/YA book. Certainly read when I was in my teens or earlier so maybe twenty five odd years ago. Main protagonists are two forest rangers or wilderness preservers or some such. They have a heat ray built into their finger with a red dot in their vision showing where it is aimed. I think at one point the good guy uses it to scare away a big cat of some description. The two become enemies and (I think) get more and more power(s)?? while combating each other. The punch line of the book is something like 'and the an-gels of haven......' maybe giving the book a twist that supposes these are precursors of biblical legends?