A good logic puzzle sharpens the mind. Here are 5 of my favourites.
Three of them are classic "river crossing" puzzles, where people and/or things have to be transported from one river bank to another, in nothing but a rowing boat. There is a PDF to download and cut out to help you solve them.
River Puzzles
The other two are "coin weighing" puzzles, where fake coins have to be identified by weight in a restricted number of uses of weighing scales.