Some of my favorites:
"We don't recycle any plastic bags, but we purify our pee."
"What's not expressly permitted is prohibited."
"To the Aunty staying upstairs: your laundry is dripping on my bed sheets."
"Please don't squat on the toilet seats and don't clip your nails on MRT."
"People put on fake accents to sound posh."
"Will I ever live till eighty five to collect my CPF?"
And if you are interested in more, check out this site: http://www.complaintschoir.org/