As mentioned above forget about devices there are just too many to cater for individually and instead concentrate on your design. It’s your design that dictates where a breakpoint should be and not some arbitrary device width that may or may not exist.
Just create fluid pages (max-width is all that’s needed for the wrapper) and then open and close the browser window and if at any point the design looks awkward then throw in a media query and make it look better. If you do that all the way down to about 300px you will collect almost every device that exists now or in the future (apart from the apple watch).
It really is a simple a process as that but of course that doesn’t mean its always easy:) Usually with a few well chosen media queries and a consistent design approach you can make the site responsive all the way up and down without ever knowing about a device.