This almost makes you want to write buggy code!

When attempting to retrieve a recordset for a web application developed in ASP.NET, I encountered the greatest runtime error ever:

Run-time error '-2147418113' Catastrophic failure
There has been a catastrophic failure. Please stand by.

Catastrophic failure! Run, children! Save yourselves!!

This now surpasses the Quartus "This operation is legal, but highly suspicious" error message I encountered in fourth year university as the greatest error message of all time.