Revo Unisntaller is one of those "must have" programs that people should have .. at a minimum the free version.. the Pro adds quite a bit more useful things with Forced Uninstall being one of them. This is a great tool to help search for leftovers of previous programs anyone has uninstalled, specially some of those AV and Firewall programs that people may test..

Definitely one of the better giveaways people can find.