1. Used alone to mean you will accept a challenge or a dare and go ahead and do something, despite possible risks. English = “I’m willing!”, “I’ll dare to do it!”
2. Used alone to express angry disregard for others comments. English = 'I don't give a damn what you think!', 'I don't care (I'll do it anyway!'), 'So what! (I'll do it anyway!'), and so on.
3. Used alone to express anger or annoyance. English = 'Damn!', 'Damn it!', 'Blast!', and so on.