I've tried to get my hands on a good Chip's Challenge editor for the longest time now.
Those I've found so far have always been very easy to use when I create the levels - the only problem is that I can never play them.
"CHIPSEXE.FILE not specified in CHIPEDIT.INI" is the message I always get when I click on Playtest, and it's getting annoying, because I want to play my own creations, not just look at them.