Uhh... Light bulbs.
My dad just installed energy efficient fluorescent light bulbs in all the lights in the house. The lights now all have a 1 to 2 second delay before they turn on. This has been very confusing to me. A lot can happen in that 1 to 2 seconds such as me thinking the light bulb has burned out and turning around to go get a new one when suddenly the light turns on. I can't count how many times this has happened to me so far.