Swiss Army
I have a bijou Victorinox pen knife on my key ring which has a small 2cm blade, an LED light, a small file/screwdriver and the smallest scissors. I flew to Spain recently (from Stanstead) and panicked very slightly that they’d nick it off me. I bunched it up with the keys and thankfully it wasn’t noticed in either direction, possibly because it didn’t have the tool to remove stones from horses hooves.