Be careful, you just might burn a hole through her dress if you stare hard enough.
Be careful what you ask for.
Be careful sitting like that, you might get a stiff neck or diabetes.
People need to be more careful when sculpturing. Though, this might have been intentional.
Dude, be careful. Girls hate it when you leave the toilet seat up.
Be careful. Viewing this picture may cause you to lose it. You'll see.