Mega Man 6 has always been in my Top 5 Classic Mega Man Games. It's very under rated too.
The Story is one of the more interesting ones (although they didn't even try to hide that Mr. X is Wily, haha). The Weapon Set, at first glance, may not seem too good. They are all actually really good, you just need to use them more to see their full potential. Music is great and the Rush Adaptors are fun.
Well, I hope you all enjoy it! :D --- The Old School Video Game King!! http://www.youtube.com/user/Redmage1987