Material Kit by Creative Tim - A Badass Bootstrap UI Kit based on Material Design.
I dont actually use bootstrap most of the time, however i love this ui kit for it! even the mouse clicks on the buttons look awesome. Very nice kit if you are into using bootstrap.
Here are some of my favourite bits from Material Kit
The Tabs look awesome, not sure how i would fit this into a design but it looks great.
The button animations, sometimes its the little things about a ui kit and these animations are on point! It even tracks where you click on the button and does a nice and quick animation, looking like a spash in a pond. Love it.
A Nice looking date picker. Now im not bagging out the JQuery UI datepicker, but hey this one is pretty sweet. Minimal and nice looking.
Even down to the tiny animations when you click on an input field it underlines, very slick.
Check out the link below to get this awesome Bootstrap UI Kit.