My "key" knives are as follows:
Serrated "Bread Knife"
I do have others. A santoku, a straight paring knife, and a smaller chef's knife than my main chef's knife.
I won't go into sizes, because that's all down to you as to what feels comfortable.
The chef's knife, as Alton Brown says, is the one I will reach for almost before I know what I am going to cook. I put "Bread Knife" in quotes because it is also very good a slicing tomatoes and the like. I eat a fair amount of chicken, and these days can dismember one of those little suckers in seconds with my boning knife.
Personally, I just don't get the paring knife thing. I bought it because everyone needs a paring knife, right? And sometimes I do, but not very often. I suppose it comes down to what I like to cook, and what I like to cook rarely presents me with anything I can't do with the three knives listed.
It drives me nuts when I see a television cooking expert cutting up vegetables with a paring knife, or peeling vegetables with one using their thumb as a backstop, but I guess to each his own.