Like gkas, I find I use the cheap one I got at Harbor Freight on sale often. Use it to check the temp of air conditioned air, the temp in the refrigerator, the tires if I think of it, the oven temp etc. Checked the temp in our little O2Cool ice fan that I bought for summertime. Fun to use and worth it to have one around.
One can use inside air temperature, inside wall temperature and outside wall temperature to calculate thermal gradient, insulation "R" factor, BTU's or Watts required to heat/cool the space. Lots of interesting stuff.
Example: Area in square feet times Difference degrees F between inside and outside temperature divided by "R" value of insulation = BTU's required continuously to heat/cool.
There are equations to calculate "R" value of insulation but I prefer to use charts. Just did some quick calculations on my parents' new town house which show the wall insulation at "R5" so no wonder their heating costs are higher than for the much larger house they sold.
People are quite innovative in finding uses. We used infrared heat guns to identify leakage past hydraulic cylinder piston seals. Cool diagnosis compared to the much greater problems in measuring flows manually for the same diagnosis.
Check the exhaust port or manifold runner temperatures to identify a cylinder which has poor power output. Works a treat, especially on diesels. Check the breakers in your household and rig breaker panels. A breaker which is heating up is on the way out. Mills and plants use this in their PM programs.
A vetrinarian bought one from me about 15 years ago to try for identifying feed lot cattle which were running a fever.....wonder how that worked out....? I could see a lot of problems with obtaining reliable results but he was in the position to try large samples and verify, plus the fact that he knew what he was doing...
A large sampling of customers did conclude that any attempted humor based on pointing one at one's better half and commenting..."You know..." will not pan out well. Just a caution.