Honesty is the best policy

These 'Honesty stamps' by Dominic Wilcox are genius. Available directly from his website, or from Thorsten van Elten.

I can think of a few choice words of my own that could be stamped all over the house:
'I'm sorry I thought that you left it on the floor because you didn't want it anymore, so I threw it away'.  Hmm a bit long, needs editing but you get my drift.