Recent examples that have amused me include when Specialized Bicycle Components released a bike named after the French town of Roubaix and its famous bike race on cobbled roads... then proceeded to start threatening other businesses also named after the town.
Or the company Peloton Interactive Inc which named its indoor spinning product after the commonly used name for a group of cyclists "peloton"... and then proceeded to start threatening bloggers for using the term to describe groups of cyclists.
What's particularly funny about the peloton case is that some other outfit in California is claiming a trademark on the term "spinning" to describe people indoors using static spin bikes... and has proceeded to start threatening small gyms for using that term.
Not sure if this is known as trademark trolling or not but I'm going to quietly trademark that term and start sending out threatening letters just in case.