I'm afraid I don't believe in what goes around comes around - by god I wish it did :). And I'm afraid I can't just walk away and let the 'offending party' off scot free.
I agree with the folks who are suggesting a nice social event, except in the week or two prior to leaving (and I'm afraid that's what it will boil down to) there should be a daily 'celebration' of your departure. So BBQs, parties, showing of peoples talents e.g. doughnuts, wheel spins etc, Saturdays/Sundays of everyone fixing their bikes in your yard, finished off with an all day/night party preferably on a Sunday into the Monday morning (or whatever their working hours are).
I've 'returned a few favours' in my time. I once put the stereo on really loud, turned the speakers to the neighbours wall, put the track on repeat and went out for the evening till the early hours and the next day, promised to repeat the exercise daily until they played ball. I also introduced the offenders to my brother
Another time, leaving a house with the offending people still in it, maggots (with meat) placed in various parts of the house where the temperatures where different so there would be flies constantly, fish pieces in little holes dotted around the house that they couldn't get into, melted lard and sand in the sink pipes, holes drilled in the rubber around the windows, tiles knocked off the roof from the inside, 2 solid days of the bath running a quiet little stream through the kitchen ceiling. Later, cress seeds dropped in through the letterbox with water sprayed in too (in early hours of morning). Ooh, there are a hundred and one ways to punish people who deserve it
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I also agree with the CCTV comment earlier - but obviously before you start 'celebrating your departure'. Some people just need to pay from all directions.
Wish I was nearer, I'd love to come and party and I bet I could come up with more 'party games' as the days went on
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Good luck with it. Turn the tables and have some fun