The idea of one of the glass ones with swirls got tossed around a bit as well, (because they are pretty) but was decided against on the grounds that glass shards = bad.

... I know that it's unlikely, but the idea still makes me cringe. ^^;;

Well, that IS how I got Saguru to torture Kaito in my BO!Saguru fic... (he broke the plug with a long pike and a hammer)