Vs. Non-Aggro -> Play Aggro?

The other option, when faced with people who you can't control very well, and who have pretty good answers to your primary plan (Slime, Nature's Claim, Primeval Titan, Valakut, OR Negate, Cancel, Celestial Purge, Revoke Existance), is to go with a secondary plan.

The secondary plan being to kill them before they get going.

In at least one of the games I'd be going first, and counters are a pretty bad answer to a resolved threat.  Also counters to non-creatures(Spell Pierce, Negate, Dispel) are a pretty bad answer to creatures.

Unfortunately, as far as burn goes, I am already using quite a bit of the relevant burn.  Anything I might bring in at this point is of the "2 damage for 1 mana" variety, which is really not very good at killing people.

Burst Lightning is okay against control, because you do it on the end of their turn with a full hand, and either way you're probably good to go.  But cards like Galvanic Blast, Punishing Fire, Forked Bolt, and the like are pretty uninspiring.  Lava Axe as a sorcery doesn't accomplish much.

Artifacts, like Sphynx-Bone Wand tend to fall victim to similar removal that is already being brought in against the PA.  Acidic Slime, Nature's Claim, Negate, Revoke Existance, Naturalize, and so on, all also kill SBW.  Some cards, like Kor Firewalker, War Priest of Thune, Flashfreeze and Dispel are avoided, but the 7cc of this monstrosity makes it prone to things we can normally play around, like Mana Leak and Spell Pierce.

This is a pretty sweet artifact though, and it falls into the same vein as the deck in general.  Cards like Steady Progress, Staggershock, Surreal Memoir, and draw spells work quite well with this.  It just costs seven freaking mana.

So, it falls to creatures to try and answer this.

The most obvious is Kiln Fiend.  It comes down early, gets a massive 3 power per spell, and kills quite quickly.  It is vulnerable to some of the same removal as PA (Ratchet Bomb, Flashfreeze, Celestial Purge), but not alot, especially if I am going first.  The turn 4 PT can't kill the KF without a Khalni Heart Expedition, so I might have that turn to kill them, with a bounce on the KHE or PT.

The next best options to compliment that are Chandra's Spitfire, Goblin Guide, Plated Geopede and Calcite Snapper.

The 3cc options are pretty slow (slow to come down -> More counterable, slow to kill).
Geopede and guide do damage fairly fast, but not fast enough to kill on their own without some serious help from specific spells/lands (and no blockers)

Kiln Fiend + Goblin Guide put up some pretty respectable T4 kill numbers with the old baseline deck (Mana Leak still in).   With an even more dedicated plan, the numbers might get even better.
(+4 KF, +4 GG/Spitfire, +4 Burst Lightning, +3Twisted Image, -4 PA, -4ITR, -4 Deprive, -3CTM or CTM).  Screwing around with that will give me something to do on the bus ride to work today...