Achievements are in:

Elephant Gun
Land the killing blow on a Circus Fleshpound with a Pistol.

Lifting a Dumbell
Kill a Circus Husk with a LAW.

Juggling Act
Drop 5 different Tier 2 weapons in one wave.

Small Hands
Kill 3 Circus Clots in a wave with the Lever Action Rifle.

Burning up the Midway
Kill 10 Circus Clots with a Fire-based weapon.

Punk'd
Unlock 10 of the 13 Circus Achievements along with any Abusement Park achievement.

The Big Hunt
Kill a Circus Scrake with a Crossbow.

Taking Down the Big Top
Kill 4 Circus Zeds in 1 ZED time chain with a Melee weapon.

Windjammer Enthusiast
Survive 10 seconds after being screamed at by at Circus Siren on Hard or above.

Assistant Homicide
Kill 2 Circus Stalkers with a Melee weapon to the back in one wave.

3 Ring Circus
Win a Long Game on Abusement Park on Suicidal Difficulty.

Dog and Pony Show
Win a Long Game on Abusement Park on Hard Difficulty.

Flea Circus
Win a Long Game on Abusement Park on Normal Difficulty.

On Top of the Big Top
Win a Long Game on Abusement Park on Hell on Earth Difficulty.

Ringmaster
Kill the "Ring Leader"(Circus Patriarch)

Seeing Double
Kill 5 Circus Crawlers with a Bullpup in one wave.

Sparing with a Master
Kill a Circus Gorefast with a Melee weapon.

Clearing Clown Alley
Kill 5 Circus Bloats in one game.