A tanto with a relatively steep angle to it. Not quite 90, steeper than 45. Good for scraping off gaskets and whatnot.
If it's a fixed blade knife, I'd make it pretty thick and I'd have a provision for striking the back of the handle.
Not saying make it like a full on chisel, but I wouldn't do any sort of easy to damage material towards the back of the handle.
Handle needs to be grippy.
Also needs a guard. No beano when you're hand slips and you get cut.
Edit: I meant "No bueno", but I think "no beano" is kinda funny, so I'll leave it.