Although I've submitted these (hopefully all of them) to the tipshop, I thought I'd post them here.
Not the "usual" run of the mill pokes, more unusual but potentially useful ones:
Stop in-game tune deteriorating as lives are lost:
Prevent Game Auto-Pausing: You can still pause it manually but it won't 'Auto-Pause' if you play without the in-game tune:
Unlimited attempts at keypad code: (well, someone *may* find it helpful)
Stop screeching noise on title screen while instructions are scrolling:
Stop screen colour cycling while intro message is scrolling: (Note: does not stop border or noise!) This best combined with the "Stop screeching noise on title screen while instructions are scrolling" pokes above if required.