Zips. No idea how they work (probably witchcraft), but they're a game changer for coats and bags.
Squirty cream. Provides the illusion of much volume in a deceptively small container. Tastier than normal cream for some reason.
Connect 4. Cracking game, even for thickos. Classic is best but can be scaled up (e.g. for outdoor garden fun) or down (for convenience when traveling). Highly versatile.