You'd be surprised how hard it is for people to grasp the obvious.
Which is why you should always be prepared with witty one-liners.
"Oh, I'm just practicing my technique for disposing human remains. Can I practice on your hands yet?"
Gives daily chores that zing of excitement. ^^
Technically not a one liner, but hey. It amuses me >:
I am so doing this next time I get asked ^_^