To limit it down to two flies is too hard for me, but I will share some of my favorites. During daytime hours I have been most successful catching bigger fish on following patterns. First is a version of the Bullfrog slider(last weeks fotw) and second a Kelly Galloup streamer, either a zoo couger or a sex dungeon depending on water clarity. I have found that anytime I am fishing less than 5 feet of water the Bullfrog slider gets the big ones attention better than any other topwater that I have tried. I will say that I have had a lot of success fishing stealth bombers as well, but in the lakes and ponds that I fish I can't seem to keep the 13-15 inch bass off of them long enough to catch the big boys(which isn't all that bad of a problem).
With all of that said, I consistently catch my biggest bass at night. I have found that many flies work well at night(gurglers, poppers, stealth bombers) but if I want to focus on catching big bass then I will throw a fly that I call the bass toad. It has such a wide footprint on the water that I feel the convinces the big fish that it is worth their time to eat whether they are hungry or not. What ever their reasons are for eating it, I really don't care as long as they continue to eat it.