Used to express extreme joy or excitement. This word is typically used all by itself, as a lone exclamation.
This can be used just after you've said or done something you're very proud of.
Can also be used if someone just got pwned, and you are rubbing the pwning in their face.
A variation of this word is "ska-BAMF!", which came into use after the animated movie Kung Fu Panda popularized the term "ska-doosh".
Ned: *showing a paper to his friend* Bamf! I just got the highest score possible on my SAT!
Barlow: Well, while you were taking 4 hours on your test, I nailed your sister in your bedroom. Bamf!
the sound effect made by the superhero Nightcrawler (from Marvel Comics' X-Men) when he teleports
Hey, look, Nightcrawler just popped in.