Create a wallet generator? Is it possible to generate private and public keys using only a calculator?   If not how many lines of code would it take to write a wallet generator, and how difficult would it be?   How would you do this?
Bitcoin Address Generator in Obfuscated Python is a fun piece  of Python 2.7 code:

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     in(map(chr,ra    nge    (123))))[W];print"Addre
       ss:",K("\0"+X.dig    est())+"\nPrivkey:",K(
         "\x80"+I(f))""";exec(reduce(lambda W,X:
            W.replace(*X),zip(" \n&amp;$@",["","",
               " ","=lambda W,",")else "])


I'd check out these two Python modules:


Bitcoinaddress 
Pybitcointools (a fantastic Bitcoin library: see the README.txt for usage)


A private key is just/can be a very large number. However it's not possible to use a calculator to calculate an address easily, mainly because:


modular arithmetic is involved
base 58 check is not a straightforward conversion
there's appended bytes and such


I'd recommend either this web app to get the next best thing.