user-select: all. Check it out in the following paragraph.
If you click on this paragraph in certain browsers (Chrome, Firefox, and Opera as of this post), the entire contents should be selected. Kinda crazy, huh? I wonder what crazy uses this could enable …
Browser support seems alright, though its opposite —
user-select: none — has much broader support. Hopefully this will see better support across more browsers soon, but the original article I learned this from also has a decent polyfill.