This calculator is cool. It's relatively inexpensive (some might argue that), yet it has a quite good resolution screen, and Z80 ASM, and BASIC programmability. Very good for games. see

Cables for attaching this to a computer parallel port are easily made using some diodes and resistors.

One feature that N-Wing likes is the ability to recall several previous entries, instead of just the previous one. This is very useful if you make a typo.