Box knife fits easily and is the best tool I've found for opening them. Slide it under, quick gentle twist and one side will pop open. That's for Kailh box switches.
MX style switches, the best tool for opening them is the top from another MX switch. Slide the latch from the top under the latch for the other and it will pop right open. Best feature is they are always the same size, so they fit perfect every time.