Sometimes you have to take the law into your own hands...
I can't tell you how much I love love love this parking citation pad from Knock Knock. Sometimes people need to be told they're an inconsiderate asshole, and these never fail me in my time of need. I keep them in my glove compartment so they are readily available. Living in Los Angeles there is no shortage of opportunities to use them. Ever.
For some reason they are no longer available on the Knock Knock site, although they have several other worthwhile versions such as the increasingly necessary douchebag citation. However they are still available through some other retailers such as Amazon.com.
They not only "make the world a better place to park" but they really boost your mood as well. Brief moments of irritation and annoyance suddenly become fun and satisfying opportunities to release your urges to micromanage.
They did omit one offense from the checklist: Illegally parking in a fire lane because you are a lazy slob that can't walk the extra 25 yards to go into the store, and you won't get a ticket because you the ARE the parking enforcement. Go figure.