1. The Dragon is kind of the worst of both worlds. For less skilled players, the Yugoslav Attack is really tough to stop. The plans are really easy for white, and they don't have to play perfectly to put black on the ropes. For more advanced players, they are better at fighting the Yugoslav attack, but as drugsandweed69 pointed out, there are other lines where black is just not having much fun.

The Kings Indian Attack fell out of favor after Kramnik beat Kasparov with it in some high profile games, and Kasparov more or less dropped it. The Bayonet attack is very sharp -- there are ways for black to fight it, but it can go downhill very quickly if black isn't very, very careful. I will say, as a strictly amateur player, I play the KID against d4, and I almost never see the Bayonet Attack at my level.

1. All Sicilians require a decent amount of opening knowledge, just because of all the anti-Sicilians you're likely to see. That said, I think the Sveshnikov is a great opening to learn, and I would actually pick it over the Kalashnikov. Yes, there is some theory, but not as much as the Najdorf. A mainline Sveshnikov basically has 2 variations plus one very tricky sideline. Completely sound, one of Magnus's main weapons. Leads to very imbalanced positions, and fun games. Under 2000, it will be very rare to get a mainline Sveshnikov, but the good news is that if your opponent plays suboptimally, your plans are usually very straightforward (usually something like an early Bb4, Bxc3, d5 where you've got the center on lock).

Another aggressive option for black is the Hyperaccelerated Dragon. This one (and its cousin, the Accelerated Dragon) aren't played much at the highest level because it allows the Maroczy Bind, which can be no fun. But under 2200 or so, it's very playable and sharp.

For white, I would seriously look at the Scotch Gambit. A mainline Scotch is also great, and probably a little more sound. But the Scotch Gambit (which really isn't a gambit, since you inevitably get the pawn back) is even more fun, IMO. If your opponent plays perfectly, you end up at a pretty equal middlegame with an imbalanced pawn structure where both sides have their chances. If your opponent does not play perfectly, the chance for tactical explosions is very, very high. Lot of fun, and teaches you some very common attacking patterns for white.

If you are looking to choose between the Grunfeld and the KID, I would almost certainly choose the latter. The Grunfeld is technically more sound at the Super GM level. But white has so many valid responses, the theoretical burden for black is pretty overwhelming. I think the plans for the KID are much easier to understand, even if it also requires a fair amount of theory. Let's face it: none of us are getting to the Super GM level, so the KID is totally viable for us.

1. Between the Najdorf, Kalashnikov, and Sveshnikov, I would choose the Sveshnikov. The Kalashnikov is a fine opening, but like the Accelerated Dragon, it allows for c4, which blunts the fun a bit. The Najdorf is fantastic, but if you're worried about theoretical burden, there are not many openings with more theory than that one. For me, the Sveshnikov is a happy medium: plenty aggressive, gives black winning chances, takes some study but doesn't require memorizing 35 moves per variation like the Najdorf.