Animal Crossing, Astral Chain, Assassin's Creed, Ace Combat... I mostly use it for Animal Crossing but I easily understand based on context what IP is refered to when AC is used.
This made me think of a dick post from a few months ago, someone here telling someone else who used AC for Animal Crossing : "the fuck are you on lmao ? AC doesn't mean Animal Crossing, it's universally used for Assassin's creed". Dude got confused that someone used AC for something that obviously wasn't Assassin's Creed and just didn't understood what he was talking about, so the other poster specified Animal Crossing, and so the Assassins dude for some reason got pissed off that AC was used for something not Assassin's Creed.
This poll really makes you realize how many IPs you could actually refer to when talking about AC.