I'm sure there's a word for this that I've forgotten. I'm looking for an English term for something that somebody likes to rant about frequently. The closest I can come is "hobby horse" but it isn't specific enough: it means something that somebody likes to talk about a lot, rather than specifically rant.
Something that could work well in the sentence "I'll never quit this [word here]" because I like to rant about it. For hobby horse I had a similar sentence in mind: "I'll never get off this hobby horse" but of course "get off" only works because of the word "horse".