I Was Just Wondering.

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Yep! MaKey MaKey comes preloaded with an Arduino sketch file that lets you control the arrow keys, space, mouse movements in all directions, mouse left and right click, and the letters W, A, S, D, F, and G. On top of that, you can fool around with the sketch file yourself and change what is controlled. Hope that answers your question!

you mean you can use shift?

There are different ways to assign various things, not just keystrokes. If I'm not mistaken, I think shift is one of those special keystrokes that you have to do differently. Alphanumeric symbols I think are as simple as deleting the keystroke contained in the sketch and replacing it with the desired keystroke. I've not gotten very far that direction at all yet, so I might be a little confused on the details there. Regardless, you can change an input to do the shift key but it may require a little extra effort. The sketch file can be toyed around with and made to do any number of things, even past keyboard functions. There's no end to however advanced in whichever direction one might explore. Short answer for tl;dr, yes it is possible to assign a MaKey control to shift key instead.

http://arduino.cc/en/Reference/KeyboardModifiers gives a list of codes used for special keys - yes it requires a little extra effort to re-write the sketch, but I had a student ask me about something similar last month too.