AC vents, to check how well insulated/sealed your windows are, and in the garage, to make sure a car's exhaust is safely cooled before touching and working on it...
Use a digital thermometer to check if your air conditioner is operating optimally, find invisible draft entry points for a DIY energy audit, and even check the temperature of foods while grilling outdoors!
Amprobe IR608A, $80 With a temperature range from -18 to 400 and a laser pointer to make it easy to pin-point the source, this is a solid all-around unit for the entry level and even a little beyond. We like the fast response time of half a second readings, the solid ergonomics and easy to read screen.
BASETech Mini 1, $30 The pen-like design, full metal construction and the very minimalistic approach to the whole package makes the Mini 1 one of our favorites. The temperature range is between -33 to 220, and you can switch between Celsius and Fahrenheit. Another nice touch: the unit automatically switches off after 15 minutes of non-use to conserve battery life.
Uni-Trend UT 300B, $40 Being able to monitor readings of -18 to 380, this IR thermometer uses the more conventional 9V battery, which equals longer operational use before battery replacement is needed. Comes with a sleep mode, low battery warning and even a laser switch for sharp accuracy. Precision is +/- 2 degrees and we find the backlight display for easy to read for outdoor use especially useful.
ELV VA 6520, $85 The ELV has the widest range in temperature measurement: -20 to 500 and super accurate resolution of only 0.3 degree. We love that it can provide different values, like, average temperature, ambient, min, max and uses an automatic range selection. Comes with a laser pointer and auto power off...and even a protective case, so bringing it anywhere is always an option.