Kudos: Home Depot.

The other day I went to Home Depot to buy air filter replacements. The filters my house uses are 20x20x1 and 20x14x1. The latter, it turns out, is an abnormal size because it can occasionally be tricky to find; 20x16x1 is the more common size. So, of course, even though I literally had what I need to buy written down on a sheet of paper, I managed to screw up the oddball filter, and only realized it after I took off the cellophane. As I prepared myself to grovel at HD and profess my stupidity, I was cut off because the exchange was a total non-issue. The customer service lady just said "no big deal" and sent me on my way.

So thanks, Home Depot, for helping out the scatterbrained population that somehow screws up a simple shopping list. :)