I love my Kor hydration vessel. I received this bottle a few years ago from a friend and it is still going! It is lightweight, BPA free which is super important. I had a steel sigg and didn't like that my water had a metal taste to it and other bottles had a cap that didn't work very well for me (ie would hit me in the face when I took a sip or required me to hold the removable cap in another hand).
This bottle has an easy clip on lip that opens with one hand, has a good size drinking spout and I like that proceeds from every bottle goes towards a specific water type charity or foundation. I just ordered a smaller 500ml version to use on the go but my 750ml Kor One is always on my desk and has a great handle for me to carry it around the office, to meetings or out and about.