What block cipher is used for CBC-MAC? What block cipher is used for CBC-MAC? DES, AES, 3DES? Or it doesn't matter?
Well, yes, it does matter; however the terminology 'CBC-MAC' does not specify which.

CBC-MAC is a generic construction that takes an arbitrary block cipher, and turns it into an object that acts like a MAC for fixed length messages (much like CBC mode is a generic construction that takes an arbitrary block cipher, and turns it into a object that encrypts variable length messages).  And, just like "CBC" isn't necessarily used with a specific block cipher, neither is CBC-MAC.

Note: CBC-MAC has issues if you try to use it with variable length messages; CMAC and XCBC are two modes similar to CBC-MAC that avoid this problem.