I've found that Fiji brand water bottles serve my purposes very well, they are square and come in 500ml and 1Lsizes. They are clear PETE, and the original labels peel off cleanly for relabeling.
I have scads of these bottles, I love them. However I have never been able to remove the label cleanly; I'm always faced with a large and extremely stubborn patch of adhesive. Rick, how do you deal with this?
Right now in Spain they're holding the Running of the Bulls,
followed by the Soiling of the Pants,
and the Burying of the Idiots.