We always pull it out and heave it on the floor in big thumps, disturbing the neighbors, and usually breaking the bag so that newly separated cubes go flying across the kitchen. And you know what? There's a better option...
... although not necessarily less violent-looking than thrashing the bag on the floor over and over. It's an ice pick — pretty simple, even if it does double as a weapon. But we've never owned one, and it's not a kitchen tool we think about very often.
Then we saw this one on Amazon: Commercial Ice Chipper, $6.95.
Anyone else have good tips for breaking up bags of ice?