Awesome, thanks! Some of those were a bit RL-ish, but still gave me a few ideas for my game. I will definitely give them a large dog with not so nice traits. And how could I forget about the "make mess" which is a nightmare even to their own parents. I was hoping for ideas not needing my sim(s) to visit the neighbor, but I guess the easiest way is to go to their neighbors' houses.
When my sim was walking past the decorative houses along the street, I wished he could stop to rob their mail boxes :) That would probably be more along the lines of a criminal, though, and not just a neighborhood annoyance.
Max and Lilith resides a flat at Grims Quarry, so the streets are already very trashy. A few more filthy objects at their gate won't really make much difference. But hey, they could redecorate their flat with only industrial stuff simply to annoy that ECO idiot of a neighbor? ;)