Oh my word. If I read "he wasn't phased by it" or the like one more time on this forum I will throw my laptop out the window.
FAZED. It's actually even easier to get right because it bloody well looks exactly like it sounds.
I am sure all ye pedants have bemoaned this very point many times already, but today I have read it no fewer than five times on MN and I am ready for a glass of 
to cope with the stress.