No one has mentioned Seamonkey, so I'll throw it out, nearly none of the endless we-can-make-it-better-and-more-like... updates that caused me to abandon then at about 4.x, I cannot specifically state memory usage is great, but I typically have 12 copies open with 8-24 tabs for each occurence on an 8GB RAM mini-ITX (iGPU).
I crash it to do the Flash-upgrade of the hour, it always returns All of my hopeless mess of windows and tabs.
If you want a browser that you can unreasonably beat hell out of, give SeaMonkey a try. Note: Netflix and other sites insist on posting a banner that your browser is old, just ignore them until they grow a clue (Netflix is the Best example of why I use SeaMonkey, it allows me to skip their hopeless new homepage and simply keep my 16 shows' tabs open, ready to watch whenever I sit down, tabs do Not update until selected, etc.).