I ♥ NY
I recently had cause to consider proprietary rights in the wonderfully iconic I ♥ NY symbol.
Designed in 1976 by Milton Glaser, the logo is protected as a registered trade mark in the US (and possibly elsewhere). The logo is used to promote tourism in New York State but more readily identified with New York City. The logo is extensively used on white T-shirts and applied to other goods. New York State has actively sought to protect its intellectual property and prevent knock-offs / derivatives.
For typography heads, the type is American Typewriter.
Designer Milton Glaser talks about his iconic creation on Big Think.