One of the best investments a hunter couldmakein my opinion! To be an effective shooter(no matter with what weapon), youMUST know your distances. A rangefinder takes all or most of the guess work out of the equation. I use a Nikon Pro 440. That one works great for me, because I bow hunt 99% of the time and don't really need anything better. You may want to step up a little bit if you expect to range longer distances more frequently.

Good Luck!