I approve of designing maps specifically for grappling.
From my experience, nothing comes close to being as amusing as a pack of three or more heavies grappling their way through
jump_squared_b2 together on a jump server -- especially that maze.
Techniques I found so far from trying that includes what I term as:
grapple-pogo (floor/ceiling),
wall-grapple,
corner-grapple,
down-grapple, and
tele-grapple (!).