A good ASCII table makes it easy to find the effects of the Shift and Ctrl keys. Like, at a glance, I should be able to answer questions like "which control character corresponds to ^V?"

On a Unix terminal, the Shift key zeros out bit 6 and the Ctrl key zeros out both bits 6 and 7. (And the Alt key sets bit 8.)

In man ascii on Linux, it's trivial to see that ^V is SYN.