Items I usually forget to bring when I go to San Diego:
Camera; forgot to bring it in January and forgot to bring it in November.
Laptop; didn’t actually ‘forget’ to take it and now regret not taking it.
Power Supply for mobile phone; I regularly forget to take this when I go away. So I’ve been trying to save the battery power by only checking the odd time.
I usually forget toothpaste when I travel and I always wonder why hotels don’t give toothpaste along with the soap and shower gels, but never enough to ask the hotel people. I suppose the answer is so obvious that I’d just look silly if I were to ask someone.