Most of my development experience has been with structured languages such as C and Java.
Given that, I feel almost naughty working with Ruby's loose typing. It's like I am getting away with something, doing something oh so wrong. For some reason it never seemed odd with shell scripts, but does here. It's both liberating and a little scary at the same time.
No compiler errors, no warnings, no runtime exceptions, no type mismatches, nothing. You can make x = 3 then turn around and make x = "dude", and then set x = FileRenamer.new with out any issues.