There are several like
Martial Coup and
Kirtar's Wrath and
Phyrexian Rebirth that create a creature for you, but I don't really think that's what you're talking about.
There are also a bunch of cards like
Novablast Wurm and
Mageta The Lion and
Myojin of Cleansing Fire that destroy all other creatures, that's a little better, but still probably not what your looking for.
There are a bunch of red spells like
Earthquake and
Subterranean Tremors that damage all creatures without flying. They're great in a Dragon Deck, and I've seen them used nicely in Izzet Wizards where there was enough flying to be worthwhile.
Plague Wind and
Dread Cacodemon are both really expensive but straight up one-sided board wipes.
There's
Wash Out, which isn't really one sided but can usually take out one or two players pretty well.
Fight to the Death is really cool with
Lure effects.
Austere Command can slot into high or low costed creature decks.
Kindred Dominance for any tribal decks.
Blood on the Snow or
Slash the Ranks if you really just need one creature.
Solar Tide is flexible, high power, low power, or just full on board wipe.
Forced March for high mana value decks.
Mandate of Abaddon for go tall.
Blood Money can sort of be if you can put those treasures to good use (recasting, reanimating, etc.)
Dusk // Dawn for higher powered creatures (plus it gets back your low ones with the other side).
Liliana, Death's Majesty for
Zombies.
A couple of the Elspeth planeswalkers do a one sided board wipe if you set them up correctly.
I sometimes use
Ritual of Soot in a deck that's a little clunky just to slow everyone else down in the early game and let me catch up.
Hour of Reckoning for tokens.
Extinguish All Hope for decks that have a bunch of enchantment creatures.
Organic Extinction and
Their Name is Death and
Scourglass and the new
Urza, Planeswalker for Artifact Creatures.
Righteous Fury or
Sunblast Angel if you're in a combat heavy play group. Really fun if you can goad everything.
Selfless Glyphweaver can turn any board wipe into a one sided one, but also has a one sided board wipe (Deadly Vanity) on the back if you just care about one creature.
Reiver Demon for artifact or black.
Winds of Rath for Aura heavy decks.
Spreading Plague is especially potent in an artifact deck though it can requires your opponents to wipe themselves, you can usually take out a color or two if you aren't completely colorless.
Fortunate Few can be surprisingly good in the right hands, especially if you're good at making deals and politicing.
Realm-Cloaked Giant for Giant tribal.
Wakening Sun's Avatar for Dino tribal.
Sivitri, Dragon Master for Dragon tribal.
And finnally,
Hythonia the Cruel for all those Gorgon Tribal decks out there.