Opera for me, and you are right, on paper its not lightweight but in actual tests, it is the fastest
http://www.howtocreate.co.uk/browserSpeed.html
So actually you get the best of both worlds, speed and features :)
BTW: isn´t Safari based on Konqueror, at least the rendering engine KHTML?
edit: and isn´t Epiphany just a frontend (simplified skin) for FF
edit2: oh contrary to popular believe Mozilla (Seamonkey) actually is faster than FF, read the link for an explanation of why)