I lived in a moderately cruddy apartment building in Palms, CA for about two years. When I moved in, it was privately owned, and the landlords were helpful and had sense (like I told them I didn't trust the 1950's stove that was in there and they replaced it with a new one). About a year in, it was sold to a property management company.
1. Unannounced visits into my apartment, followed by a written complaint about what a mess my apartment was, and that I needed to clean it. Uh, my apartment was cluttered, because it was a dinky little space. Kitchen and bathroom were spotless. No food trash, etc. And beyond that, it was no one's flippin' business! And it wouldn't have even been seen if they hadn't gone inside without my permission (and I have cats that could've escaped).
1a. Unannounced visits by a dude while I was in the shower - walked out of the bathroom nearly naked...
2. Complaints about how I kept the OUTSIDE of my apartment - my window was dirty. Yeah, the window was dirty because your gardeners would splash water and mud on the window when they watered. Plus, isn't the outside the building management's responsibility?
3. Garbage disposal of doom - it broke, I called. And called. And called. The sink was full of yucky water and food, of which I tried to remove as much as I could. About two weeks later, after multiple unanswered calls a day, I started getting roaches. I kept calling, kept calling. About a month in, they finally replaced my garbage disposal, and exterminated for roaches. They then tried to bill me for the extermination, because I caused the roaches, using #1 as a reason.
4. The kicker - the last month when I was in my place, just before I bought my new place and gave notice. Sitting in the bathroom, I heard a sound of drip drip drip. Look up at the shower ceiling, and notice water damage. Being a good tenant, I call it in. They come and look and ask me WTF I did to cause water damage on the ceiling. Completely blamed me. Didn't do anything about it. A couple of weeks later, I hear something falling into my tub...that would be part of the ceiling above my shower. And more consistently running water from above. So long story short - I spent the last couple of weeks in my apartment with leaking toilet water from above, an unusable shower full of drywall, and the need to use an umbrella every time I used my toilet. Luckily I was mostly staying at my boyfriend's apartment at the time. At this point, I didn't really bother to have them come in and deal with it, because I was in the process of moving.
Amazingly, after basically sitting my butt in their office and refusing to leave until they cut me a check, I got most of my deposit back. I really should've pursued extra money, but it wasn't worth my time, which was much happier spent setting up my own place...