Firefox is my browser of choice, as nice as chrome is there are just some firefox plugins I couldn't function without.
the about:config is another story as well as userchrome and those are powerful but I could live without them as difficult as that would be.
For example there's an add on called too many tabs, I love it for a multitude of reasons. The basic idea is that I keep a lot of tabs open as I'm sure you do, and they stay session to session till I'm done with them, but this is a serious waste of resources and processing. So too many tabs (tmt from here out) works in a way where I don't have to clutter my bookmarks. Because that was the only other option is to bookmark and close it them hope you remember to get back to it later. Instead I get a bar that I can drag and drop tabs into with various selectable categories. This way I can keep temporary tabs around without bookmarking them, then bring them back, use them and close them. It's particularly useful for my udk reference pages that I'd rather not bookmark because they're specific examples I won't need in a week or two but I don't know how often I'll need them in that time. I also keep an imdb section for upcoming movies to remind me when they're coming around and then when they do I just take them off the list. Sometimes I'll keep searches around so I can check for updated info quickly, or continue a search at a later date if I'm having a particularly difficult search. Which I should mention I'm fully aware of all the advanced operators for google search, but some things simply can't be found so easily.
Then there's adblock plus and flashblock which we all know and love. Download statusbar which moves the download window into the statusbar, just because I found it infuriating and this looks nice. Extended statusbar which gives more detailed info on the pages you're visiting such as how quickly you're getting info, how many pictures are loaded out of how many are on the page, etc.
Keyconfig for swapping out hotkeys and making new ones. It might seem silly at first, but sometimes I like my hotkeys a certain way, or need a special feature to be quickly accessible and this helps me do that.
Menu Editor lets me pick and choose what's in the menu and context menu and what order everything is in. Much more powerful than you might realize, especially when combined with Tiny Menu which condenses your entire main menu into a single drop down. Instead of File, Edit, View, etc you just get one nice dropdown, and optionally you can still have some things outside that menu if you just wanted to condense one or two things, but I opted to have all but my bookmarks in it. I then combine this with userchrome.css to put my addesss bar next to the menu to give me more screen space because I'm not such a big fan of fullscreen even with the full fullscreen add on to autohide everything it's just not my style. Speaking of style there was a nifty plugin I don't have anymore but I used to have fun with called Styles that allowed you to tweak every page you visit with your own css, or just certain pages, or you could simply modify the css present on a page if you wanted to change out fonts or colors or backgrounds it was all yours to play with.
Another add on I love is tab utilities, and tab kit however tab kit isn't updated for v9 and tab utilities might be implementing more or less the main feature I use in tab kit so I might be dropping it all together. The tab grouping option in tab kit was what I loved about it really. Tab utilities just has a lot of tab features that FF was missing. The current tab grouping options in FF and tab utilities is vaguely nice but way more effort than what was in tab kit where it simply grouped how you chose automatically, I prefered by site for example, and then when you were on a different page not in that site the tabs would condense into one and have a little plus marker to expand them back when you wanted back in. You could also hole the right click on your mouse and scroll through tabs quickly and if you selected one of those tabs sites it would automatically expand back open.
Session manager, simply one thing FF should've hat right off the bat really, at least as an install option. I love how easy it is to save and resume your sessions this way and be confident that your session was not only saved but if something happens you have several backups from previous sessions plus your own custom save sessions. The built in just doesn't do a good job of confirming your saves and is a little flimsy in the actual saving process, I'd lost quite a few sessions before I found session manager and now I'll never go back. One of the great features it has is actually the ability to pick and choose which tabs to restore if for example you get a page that causes FF to crash every time you can tell session manager not to load it anymore.
Personas if you want to add a little flare allows a little play room with your browser without completely changing the theme, it's like a little bit of wallpaper for the browser. Now the next couple are probably on chrome for sure, while some of the others might also be I'm not so sure, I try to keep my chrome as free of everything as I can when I just need a quick search for something or don't need all the features I have in FF. Simply put I think of my chrome as a little speed racer quick and nimble it helps me get things in a hurry. FF on the other hand is my heavy lifter, my powerhouse of a browser that I use for serious work or long days on the net. Things like the real player recorder and tineye reverse image search are nice little add ons. If you want to download a video from the net to watch later offline or make a composite of do a little video editing w/e real player is great at grabbing things. It also has a built in converter to change file formats to mostly anything, including stripping the vid and just giving you the audio, for example if you wanted to listen to a lecture in the car you could use real to rip the audio and put it on a disc (who uses discs anymore?) or mp3 player. And if you're looking for information or sources of a particular photo or video there's a lot of various such "reverse engines" out there but tin eye is the most powerful image based reverse engine I've found so far, it's rare it can't help me find the info I'm looking for on a picture. Of course google is liking this idea and their reverse search is pretty powerful as well, but it's not as precise as tin eye yet so it'll get a secondary recommend even though it's not an add on... Which is really where tin eye shines, just right click and reverse search, you don't have to go anywhere or do anything else and it'll look for you and have results in a second.
These are just some of the add-ons I use, of course with all these I do have a couple extra seconds on startup of the program but I keep track of that to make sure things aren't too cluttered. I highly recommend you give some of them a try, they'll improve your internet experience a lot. One last shout out to chrome though, their built in session manager is consistent, high quality, and while it doesn't confirm I've never lost a session or had to worry about it, if you don't like add ons but need a great built in session manager chrome is king.
Unrelated... I used to be a serious Final Fantasy junkie, but ever since the merger with enix its all been downhill and I can't honestly recommend any SquareEnix FF games, only SquareSoft FF games, but if I had to say one that wasn't horrifically bad it would be FFXIII or Crisis Core on the PSP. I'm not including movies because Advent Children was pretty BA even if it was a little weaksauce.