Fate/Zero

Pretty simple question, considering we've seen him have multiple masters from Tokiomi, Kirei, Hakuno, Tine, and we all know how much he hated Tokiomi and honestly who can blame him, compared to how he is with Tine and Hakuno. So of course the obvious question is who would make for a good master for Gil?

Okay what's the deal with Waver's PTSD from the fourth war, because don't get me wrong I understand it he was young when he was a master, and him being scared by Gilgamesh makes sense, but why Artoria? I haven't read Case files so I don't get why he's so scared of Artoria when you would think he would be far more terifed by Gil. So what's the deal