Oh man, my old girl loves to attack the vacuum. She will chase it and grab it and try to pull it across the room. I usually end up crating her while I run it because she goes crazy for it. She also does some other really cute things, like when she wants her belly rubbed, she paws her ear. Once I notice and rub her belly, if I stop, she'll smack her ear with her paw again and this motion repeats until shes had enough belly rubs. She also likes to sit in the bathtub. She waits for water in there and would drink water from the tub instead of from her bowl. Now that she's a bit older she gets stuck in there sometimes and it always gives me a good laugh having to get her out. I can usually hear little nails pitter-pattering on the tub from another room. And she gives hilarious high-fives. She jumps in the air and slams both paws into my hand. If I hold up two hands, she'll put one paw in each. Lastly, she destroys toys. I'm not certain if I would call this a quirk or not but she rips them to shreds and then rolls around in the fuzz.
Her high fives: