On to Red. I like Cave In, a red ACC sorcery. Basically, you discard it and remove another red card from the game to deal 2 to all creatures and players. It can be a little faster than Steam Blast. I like Crash, the 2R instant that you can also pay for by sacking a Mountain that destroys an artifact, and it's big brother Pulverize, although this one takes two Mountains but destroys all artifacts. Unfortunately, it's a sorcery. Speaking of artifact kill, there's Hammer Mage, whish is a Meltdown on a stick, a 1/1 for 1R that makes all your cards into Meltdowns. Except that they're instant Meltdowns. Red's Legate sucks.
Lava Runner is cool, a 2/2 with haste for 1RR that makes your opponent sac a land if they target it. I really like Kyren Negotiations, this 2RR enchantment lets you tap one of your creatures to deal a point to a target player. Just the card to drop when you can't kill your opponent with your initial rush and in a few turns you win.
There's the mighty Lithopage, a 7/7 house for 3RR that chews up your Mountains. Moo. Plus it can't be Treacheried or Briberied, usually. Is it wrong to wish that it also trampled?
Of the Flailing Creatures, I like only the Soldier, the 2/2 for an R that any player can give +2/+1 or -1/-1 for one mana, repeatedly. Throw in some red land kill (Pillage, Stone Rain, Avalanche Rider, Seismic Mage) and this creature can get very annoying. Plus, unlike other red weenies, this creature is a threat later in the game as well; especially if you've had some good results with land destruction.
One of the red Spellshapers, Seismic Mage, is some good. Maybe R/G land kill will make a comeback with this card. Oh, it's a 1/1 for 3R that makes all your cards into instant speed Stone Rains, basically. With Pillages, actual Stone Rains, Avalanche Riders, Argothian Wurms and son, you could have some fun. Plus, the Hammer Mage (aka "Meltdown Mage") can control artifact mana very efficiently.
Someone said they like Tectonic Break, the XRR sorcery that makes each player sac X lands. I guess you could call it an expensive red Armageddon, sort of, provided you're two lands ahead of your opponent. Actually, that's not too hard to do in red.
I like the Two-Headed Dragon a lot. Yeah, I know no one will ever play it because of Bribery and, especially, Treachery, but man is it good. For 4RR, you get a 4/4 with four, count 'em, FOUR, special abilities. It pumps, it flies, it can block two creatures, it has to be blocked by at least two creatures. Be a hero(ine), play it with Last Ditch Effort or Brand, so that blue can't steal it. O.K., play with Lightning Dragon, ya' weenie.
The most amusing red card I've seen in a while, probably since Illicit Auction, is Thieve's Auction. This sorcery makes players set aside all permanents, then take turns choosing from among them and to bring them back under their control tapped (read the card). Caster chooses first. Man, is this big fun? If only it weren't 4RRR. I really like it for fast red decks against fat green or pro-red, as a reset, although I guess traditionalists would point out that Jokulhaups is better for this. Wait, Illicit Auction is back also. Do I sense a theme? I guess I broke my promise to only talk about serious tournament-worthy cards. Oh well.
Squee, Goblin Nabob, the 1/1 goblin legend for 2R that comes back to your hand from the graveyard at the beginning of your upkeep, might as well not have been a creature at all. Squee's special ability meshes well with the various creatures that require discarding a card from your hand, like Spellshapers. Squee is also nice with Masticore. Once you get this going, you don't have to give up all your draws to feed the Masticore. No doubt there are a lot of potential uses for this card's ability, just not as a creature, unless you play R/G and use Food Chain.
White has Rebels to match Black's Mercenaries. See my discussion of Mercenaries. Note, however, that I like the Rebels a lot better because many of them, mainly the non-fetching ones, are fine creatures in their own right. There's a couple of 2/2's for 1W or WW. There's a pro-red and a pro-black 2/1 flier for 2W. Then there's Cho-Manno ("Cho Mama"), the 2/2 Legend for 2WW that prevents all damage dealt to it. There' Rappelling Scouts, a 1/4 flyer for 2WW that can gain protection from any color for 2W. Of the fetching ones, the one I like and would actually play is the Ramosian Captain, the 2/2 first striker for 1WW that lets you fetch all the four cc or smaller Rebels, i.e. the good ones. It's decent enough for the cost by itself and it has the capacity to get the other good Rebels. Mike Dewey, King of the (white) Weenies, is currently tuning a Rebel deck, but don't let that discourage you. It still might be worth trying.
Devout Witness, a 2/2 for 2W that makes all cards in your hand into Disenchants, is a solid white control card. I really like it. A lot. Substitute it for Disenchants. White Weenie is looking very attractive.
Crackdown, a 2W enchantment, acts like a Meekstone for non-white creatures. You can play with Crusades and Glorious Anthems out the wazoo and still control your opponent's larger creatures. Speaking of 2W enchantments, Arrest is not bad. It's a Pacifism plus you can't use any of the cratures' abilities either. Come to think of it, there's been many times when I've wished Pacifism could also shut down creature abilities as well.
Ivory Mask is a powerful enchantment for 2WW that prevents its caster from being the target of spells and abilities. I wonder if it would work in a Replenish or Enchantress deck. It helps U/W control decks which, in this slower environment, may see a comeback. Another powerful defensive enchantment is Story Circle. For 1WW you can choose a color, then spend a W any time to prevent all damage from one source of that color. It's like a very flexible C.O.P.
The last noteworthy white card I want to discuss is Armistice, a 2W white enchantment that lets you spend 3WW to draw a card and give your opponent three life. I'm not sure what to make of this card. I think Scrying Glass is the better choice for the typical white deck. It's cheaper, you opponent doesn't gain life and you get to see their hand. I mention this card because card drawing in white is a rare phenomenon.