I can think of grabbed, hidden, undetected, and concealed, and of course recovery checks when you’re dying, with its weird rule where it’s a flat check but not a set DC.
What else calls for a flat check?
3 points
The other one of the top of my head is Stupefied which imposes a flat check to successfully cast a spell
2 points
1 point
I just found one more. Overcharging a wand.
