I admit it's not a "big one", it's the best kept browser secret on the web.
See
http://www.pcadvisor.co.uk/news/index.cfm?NewsID=10455
where they talked about just that a few months ago.
I started using it several years ago when I was trying to stop annoying pop-ups in IEx, and googling around, trying several pop-up blocker extensions/toolbars, always found that the blocker either didn't work well, or had side effects (design features) which were as annoying as the pop-ups.
Then one hit, pointed at this Maxthon thing which turned out to be a whole browser not an add on, and contained all the features conspicuously missing from IE.
Being based on the IE engine, it was very familiar and was infinitely customizable, and rendered all my favourite websites exactly as I expected (sadly Firefox Opera et al, would all render pages slightly differently)
The particular reason I wanted all those features was for online quiz entry in a UK TV show, which I calculated was a good statistical punt (it was a premium rate phone line game, but had free web entry).
One particular feature of maxthon was a toolbar button that can dynamically switch tab behaviour, without the need for a Ctrl or Shft input, and I used this to good effect, to rapidly reuse one tab for entry without having to re-enter my details on each entry, which enabled me to machine-gun entries into the system up to their max limit.
My analysis of the binomial probabilities involved proved correct and I won the competition twice, netting £1750 ($3500), before the program was pulled off air after an internal production company scandal about rigging the game.
I put my success down entirely to the efficiency with which Maxthon allowed me to do things which weren't possible with IE, Firefox or Opera (I did try them). I actually won the first time on the very day that I first installed Maxthon.
How many browsers are not just FREE but actually pay YOU money ?