I've had some Sugru for a while, but I'll be honest, apart from custom fit headphones the applications for it have been a bit limited.I did however have a relentlessly leaking tap; that had resisted no less than 3 sets of washers, including ones supplied by a plumber. In the end Sugru worked extremely well to fix it: the tap now turns 'off' with minimal effort, does not drip, etc.
Given the size and shape of the washer plus the opening it had to seal, it was just a matter of putting ~3-4 extra mm of depth on some cheap washers, curing, and letting the tap itself 'cut' the sugru to size by turning it fully off - the edge of the seat acted like a cookie cutter.
Since the majority of sugru is just sillicon, this fix should be fairly stable for the life of the tap - it acts as a plug or cork, rather than a 'lid' like a standard washer might.
