Black Holes are dangerous obstacles found in Super Mario Galaxy. If Mario (or Luigi) falls off of some ledges or misses his targert with something like a Sling Pod, he could be sent spiraling into one. Doing so make him lose a life. In the level Bowser's Galaxy Reactor, after Bowser is defeated, his sun will turn into a black hole and start sucking up Mario, Princess Peach, Bowser's fleet, Princess Peach's castle, and the Comet Observatory. The fleet is destroyed, and the white Luma is sucked in, but the other Lumas stop it before it does any more damage.
A black hole also appears in the Mario Party 6 mini-game Black Hole Boogie.