I'll put this one here because we're in the digital age, but the cold/flu thread made me think about it...
Not wanting to go to school, so I'd take the mercury thermometer (oral only, no ghey anal of course) and hold it next to/touch a good ole environment killing 100w light bulb which would rocket the mercury up, then carefully shake the thermometer down to an acceptable temperature level of proper "fever" and take it to Mom. It worked. She never gave me a wink or questioned it, never got the chance to ask her if she knew (and I'm guessing she had to know, but maybe not), but the couple of times I did it (elementary/junior high years), she called in sick for me.