After using the i3 window manager for several years, I finally stumbled onto the hide_edge_borders option, which lets windows butt up against the edge of the screen instead of leaving a 2px gap on every side. Apart from the minor screen-real-estate savings, this means my browser "new tab" button is always in the bottom-right corner so I can just fling my mouse at it and hit it every time.

Yay for Fitt's Law!