Most valuable sockets

If you could only put 3 gadgeteer sockets on a board what would be the 4 most valuable?

(Besides the socket for programming.)

You can combine types, like A and P. Take a look at cerbuino.

If I could only have 3 sockets then it would be impossible to pick 4… :wink: My pick of socket types would be I, S, X, A.

No U sockets? For me, it would ve U, I, S