I look her in the eyes romantically, with a touch of mischief, and state "you're a very useful girlfriend".

I only do it a couple times a year at most.

The look of disdain is priceless.

She knows I love the hell out of her, and the anti climax is brilliant.

"What am I?! Your bloody house cleaner?!"

Then we laugh. Cuddle. She feigns a cold shoulder.

Too much fun.