I just got, as a 'stocking stuffer,' a whiskey stone. It's a small cube of granite that you freeze in your ice tray (or wherever you think you can find it again) which, when placed in your glass, keeps it cold without diluting it further.

Now, notice I used the whiskEy spelling, as no one in their right mind could possibly EVER chill the 'good stuff.'

Any of you folks ever use this? I'm also wondering about porosity--it's not polished. I suppose I just need to rinse it really well before refreezing?