I managed to find a decent sized game here: http://jonripley.com/i-fiction/games/LostKingdomBF.html
The game was originally written in BBCBasic at 2.74KB, but the BF is 2.08MB
Too bad it's too large for the calc

Fibonacci Sequence!!!!

BF,FIB
>+                 ;sets cell 0 as 0 and cell 1 as 1, to start the sequence
[                  ;holds entire sequence loop in brackets
[>+>+<<-]          ;duplicates cell 1 into cell 2 and cell 3
>[<+>-]            ;scootches cell 2 over to cell 1
>[<+>-]            ;scootches cell 3 to cell 2
<<<[>>+<<-]        ;adds cell 0 to cell 2, deleting cell 0, and setting cell 2 as the current answer
.>,[-]<            ;displays current answer, then asks for input, then deletes inputed cell, for a pseudo pause
>[<+>-]            ;scootches cells over again
>[<+>-]<           ;now all cells are scootched and set for another loop
]                  ;ends loop


whoops! i forgot i didnt show numbers. my bad.

Oh god, I hate brainfuck so much

And......
YEAH!
Brainfuck is named quite well, it fucks with your brain.

1337 Posts!!!!1!111!!!!

got it! fibonacci sequence, printing the decimal values of the numbers. it only goes up to 255 though, since its hex, so after 233 the fibonacci seequence gets wonky. I didnt write the part that prints the decimal values, so i enclosed it in asterisks. heres where i got it http://mazonka.com/brainf/


>+
[
[>+>+<<-]
>[<+>-]
>[<+>-]
<<<[>>+<<-]
>[<+>-]
>[<+>-]<

[>>>>>+>+<<<<<<-]>>>>>[-<<<<<+>>>>>]>              ;copies cell 1 to cell 5 and 6, then moves cell 5 back to cell 1, in essence just copying cell 1 to cell 6, giving space for the decimal printer

***************************************
  [ -<++>
  [ -<+>
    [ -<+>
      [ -<+>
        [ -<+>
          [ -<+>
            [ -<+>
              [ -<+>
                [ -<+>
                  [ <[-]+> ->+< [<-] ]
  ]]]]]]]] >]

<<[>++++++[<++++++++>-]<-.[-]<]
***************************************

<<<<                                                ;moves pointer back to cell 1 for sequence
>,[-]<
]

That, combined with the fact that z80 ASM has nice mnemonics, like add, sub, ld, etc. while BF has only 8 symbols and can't have subroutines that make for nice, structured programming
I doubt the existence of a good number of people who can easily understand what a piece of BF does.

What does this do? (No running it )
>+++++++++[<+++++++++++>-]<[>[-]>[-]<<[>+>+<<-]>>[<<+>>-]>>>
[-]<<<+++++++++<[>>>+<<[>+>[-]<<-]>[<+>-]>[<<++++++++++>>>+<
-]<<-<-]+++++++++>[<->-]>>+>[<[-]<<+>>>-]>[-]+<<[>+>-<<-]<<<
[>>+>+<<<-]>>>[<<<+>>>-]>[<+>-]<<-[>[-]<[-]]>>+<[>[-]<-]<+++
+++++[<++++++<++++++>>-]>>>[>+>+<<-]>>[<<+>>-]<[<<<<<.>>>>>-
]<<<<<<.>>[-]>[-]++++[<++++++++>-]<.>++++[<++++++++>-]<++.>+
++++[<+++++++++>-]<.><+++++..--------.-------.>>[>>+>+<<<-]>
>>[<<<+>>>-]<[<<<<++++++++++++++.>>>>-]<<<<[-]>++++[<+++++++
+>-]<.>+++++++++[<+++++++++>-]<--.---------.>+++++++[<------
---->-]<.>++++++[<+++++++++++>-]<.+++..+++++++++++++.>++++++
++[<---------->-]<--.>+++++++++[<+++++++++>-]<--.-.>++++++++
[<---------->-]<++.>++++++++[<++++++++++>-]<++++.-----------
-.---.>+++++++[<---------->-]<+.>++++++++[<+++++++++++>-]<-.
>++[<----------->-]<.+++++++++++..>+++++++++[<---------->-]<
-----.---.>>>[>+>+<<-]>>[<<+>>-]<[<<<<<.>>>>>-]<<<<<<.>>>+++
+[<++++++>-]<--.>++++[<++++++++>-]<++.>+++++[<+++++++++>-]<.
><+++++..--------.-------.>>[>>+>+<<<-]>>>[<<<+>>>-]<[<<<<++
++++++++++++.>>>>-]<<<<[-]>++++[<++++++++>-]<.>+++++++++[<++
+++++++>-]<--.---------.>+++++++[<---------->-]<.>++++++[<++
+++++++++>-]<.+++..+++++++++++++.>++++++++++[<---------->-]<
-.---.>+++++++[<++++++++++>-]<++++.+++++++++++++.++++++++++.
------.>+++++++[<---------->-]<+.>++++++++[<++++++++++>-]<-.
-.---------.>+++++++[<---------->-]<+.>+++++++[<++++++++++>-
]<--.+++++++++++.++++++++.---------.>++++++++[<---------->-]
<++.>+++++[<+++++++++++++>-]<.+++++++++++++.----------.>++++
+++[<---------->-]<++.>++++++++[<++++++++++>-]<.>+++[<----->
-]<.>+++[<++++++>-]<..>+++++++++[<--------->-]<--.>+++++++[<
++++++++++>-]<+++.+++++++++++.>++++++++[<----------->-]<++++
.>+++++[<+++++++++++++>-]<.>+++[<++++++>-]<-.---.++++++.----
---.----------.>++++++++[<----------->-]<+.---.[-]<<<->[-]>[
-]<<[>+>+<<-]>>[<<+>>-]>>>[-]<<<+++++++++<[>>>+<<[>+>[-]<<-]
>[<+>-]>[<<++++++++++>>>+<-]<<-<-]+++++++++>[<->-]>>+>[<[-]<
<+>>>-]>[-]+<<[>+>-<<-]<<<[>>+>+<<<-]>>>[<<<+>>>-]<>>[<+>-]<
<-[>[-]<[-]]>>+<[>[-]<-]<++++++++[<++++++<++++++>>-]>>>[>+>+
<<-]>>[<<+>>-]<[<<<<<.>>>>>-]<<<<<<.>>[-]>[-]++++[<++++++++>
-]<.>++++[<++++++++>-]<++.>+++++[<+++++++++>-]<.><+++++..---
-----.-------.>>[>>+>+<<<-]>>>[<<<+>>>-]<[<<<<++++++++++++++
.>>>>-]<<<<[-]>++++[<++++++++>-]<.>+++++++++[<+++++++++>-]<-
-.---------.>+++++++[<---------->-]<.>++++++[<+++++++++++>-]
<.+++..+++++++++++++.>++++++++[<---------->-]<--.>+++++++++[
<+++++++++>-]<--.-.>++++++++[<---------->-]<++.>++++++++[<++
++++++++>-]<++++.------------.---.>+++++++[<---------->-]<+.
>++++++++[<+++++++++++>-]<-.>++[<----------->-]<.+++++++++++
..>+++++++++[<---------->-]<-----.---.+++.---.[-]<<<]If you do run it though, it's a fun program (not mine, though, I must say)
My only point is that things get confusing really quickly
But who knows, you probably understand this language better than I do