Chromium
Used by 14 peoplechromium.org ↗

“I'm still emotionally attached to compiling Chromium, so I need at least 16GB of RAM.”
Monica Dinculescu Interview, Emojineer (Chrome, Polymer) · via Uses This 

“It's based on Chromium, so to customize it you can inspect it just like any other web element.”
Zach Holman Interview, Web developer (GitHub) · via Uses This 
“Nightly build of Chromium full-screen on the right-hand (tallscreen) monitor.”
Mark Pilgrim Interview, Developer & standards advocate (Google) · via Uses This