I know you're all crackpots like me; so lets have them.
One of mine is gas. I hate gas, gas cookers etc. I sometimes think when I turn on a light in a darkened room there will be an undetected gas leak and i'll die in a massive explosion.
Another is using loo paper in McDonalds or the train station and suspecting i'll get jabbed with a used needle stuffed up there...
I also have a very irrational phobia of missed calls, unanswered voicemails or letters. I always suspect the very worst and i'm on edge until I know what's what.