Welcome to the forum. As Smoke said there are some crazies. Watch for the Squirrel, he's mean, ugly(I mean real ugly), and smelly! Yup you're monitor will emit a smell!
For the price the Varizone is probably the best. However, if you don't mind spending more then put on a good quality rifle scope (I have a Leupold VariX3 on one of mine). If you want to put a dot on your target try the Bushnell Halo. It is a minute sized dot, small, brighter than red dot scopes, and light weight. Most of the red dot scopes have 3 to 6 minute dots. Just like a rifle you buy the best optical device you can afford. The Varizones are kinda delicate and not problem free but again probably the most popular xbow scope.