I don’t encourage insulting, but the most durable ones (and, by some peoples’ definitions, more tolerable, often because they appeal to some kind of truth) are usually the oddly creative/specific ones. For example, there’s the famous Shakespeare line “I’d engage a battle of wits with you, but I see you’re unarmed”. Basically what Dirty Harry and Sgt Hartman do. In contrast, you have things like the “F you” and the “a**hole” which just seem like you’re throwing what you can find.