Under Firefox, I consider Adblock and Noscript to be essential. I also use Tab Mix Plus (so that I can change tabs by hovering the mouse over them, without need

Under Firefox, I consider Adblock and Noscript to be essential. I also use Tab Mix Plus (so that I can change tabs by hovering the mouse over them, without needing to click, and also for the changing of tab color when I haven't look at one), Tab History (useful from a usability standpoint, and because I often forget which tab I was originally in), and Autopager (so that I don't have to load pages as often/wait for them to load, if it's linear stuff - like articles). Under Chrome, I'm only using one, Adsweep, which doesn't work nearly as well as Adblock, but is better than nothing.