I'll answer this for characters, instead, since it's a fun one:
- Jon Knight: Blood. It's the weirdest phobia a mortician can have, I know, but seeing living people bleeding makes him nauseous.
- Paul Feistus: Solitude. Not the relaxing, Walden sort, but the kind where you're cut off from everything and everyone involuntarily. You get like that after being in an asylum for a decade or so.
- Ral O'Dailigh: Loss of control, pure and simple - the thought that he could do something to hurt those around him and not care is devastating.
- Buster Heywood: Being caught or trapped in any fashion. ANY. He's a neurotic little bugger, and I'm still in the process of unraveling where, exactly, that comes from.