Good Free Duplicate Finder Program

What do you people use that's a good free duplicate finder?

Preferably small, efficient, and simple to use.

Python

Perl>Python

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opera

>>5
Fail

Opera fanboys are killing their brand like the Mac fanboys

>>6
Opera developers already killed opera. We're only messengers.
Opera sucks sure there's an ebuild for opera but it just get dropped to /opt, it's statically linked, and it's CLOSED SOURCE, which means that it is a BINARY package.

>>7
Opera doesn't do much worse or better then what other browsers can achieve.
It still a toss up depending on what you use it for.