Not-so-phantasmal Killer
Having seen our Rogue die earlier from a Phantasmal Killer, I was a little concerned when a similar illusion appeared in front of my face in the midst of a battle. The Phantasmal Killer is an illusion that presents you with your worst nightmare. You make a Will saving throw to disbelieve in the illusion; if you fail that you have to make a Fortitude saving throw or die of fear.
The illusion starts to take shape in front of my Monk's face.
GM: 'Make a Will saving throw.'
I throw the D20 and succeed in saving against the Illusion.
GM: 'Okay, make a Fortitude saving throw.'
Me: 'What?! ...'
GM: 'Oh yeah, you made the Will save. Never mind.'
But it was too late. My body was slumped over the table after I had failed the Will save and thus believed I needed to make the Fortitude save. I was dead from the fear of having my character die instantly.