I love writing assembly code in RPN with Forth macros!
You can write FORTH code with loops and conditionals and any kind of logic and parameters, that dynamically assembles machine code! Much better than your typical macro assembler.
Here's some 6502 assembler for an Apple ][ SUPDUP terminal emulator that does ram card bank switching:
http://www.donhopkins.com/home/archive/forth/supdup.f
Here's some Forth 68k assembler that draws lines on a weird Sun-2 CGONE graphics board.
http://www.donhopkins.com/home/archive/forth/cg/bline.f
Mitch Bradley's 68k forth lets you use interactive conditionals and loops in the top level outer interpreter!
I think he wrote a paper about that feature, which I might be able to dig up ... Here's something related he wrote about refactoring the outer interpreter, but not what I'm thinking of:
https://groups.google.com/forum/#!topic/comp.lang.forth/lKQj...