Day sixteen of RPG A Day looms on the horizon, and the question it presents is--
Which RPG Do You Enjoy Using As Is?
I'm going to be a pain again, and say, "most of them."
That's not to say I don't like optional rules. I love the little rules widgets in the DMG, and the some of the optional rules that come up in the career books in Fantasy Flight's Star Wars games. The larger and more complex the rules set, the more likely I am to look at optional rules. But most of the time, I do want to get an impression of how the rules are suppose to work before I start tweaking.
This wasn't always the case. There are times I want to go back in time and slap myself silly over the way I ran 3.5. I had all kinds of houserules to try to evoke 2nd edition quirks here or there. I will say, compared to another GM that we had for our group, I have long had a deep and abiding love of campaign standards, so I wasn't making changes on the fly, only at the beginning of a campaign, or when we had a natural break where I could poll my players and ask "hey, how does this sound when we start back up?"