I have been Googling this like crazy and found no answers whatsoever to this question everyone seems to be asking. Well, about 5 minutes ago I figured it out.
First off, your newgrounds achievements don't count torward you getting the artifact 19. Press the P button, and select achievements. It is THESE achievements you need to get. A main reason why you probably got the newground achievement but not the Thing-Thing acheivement was because you didn't die. keep in mind you need to die for any Thing-Thing achievement to register. Exiting the window or leaving to the main menu mid-killing spree cancels any achievements you may have gotten.
"So how do I get my Artifact 19?" you ask. well, look at this guide:
//beretta bonuses
9mm Warrior - 100 (15 kills with 1 Beretta)
Sidearm Focus - 250 (30 kills with 1 Beretta)
Beligerantly Understated - 1000 (50 kills with 1 Beretta)
//dual beretta bonuses
2 Is Better Than 1 - 100 (25 kills with dual Berettas)
Death In Stereo - 250 (50 kills with dual Berettas)
Deciple Of Woo - 1000 (100 kills with dual Berettas)
//magnum bonuses
Handcannon Proficency - 100 (25 kills with the Magnum)
Soar Hands - 250 (50 kills with the Magnum)
Do Ya Feel Lucky? - 1000 (100 kills with the Magnum)
//thompson bonuses
I Let My Gun Do The Talkin, See? - 100 (25 kills with the Thompson)
You'll never take me alive, Coppers! - 250 (50 kills with the Thompson)
Chicago Memoir - 1000 (100 kills with the Thompson)
//glock 18 bonuses
Safe, Semi, KILL - 100 (15 kills with 1 Glock 18)
Spray and pray champ - 250 (30 kills with 1 Glock 18)
Abundance Of Ammunition - 1000 (50 kills with 1 Glock 18)
//dual glock 18 bonuses
Who needs accuracy? - 100 (25 kills with dual Glock 18s)
Wall of fire - 250 (50 kills with dual Glock 18s)
Bullet hose wrangler - 1000 (100 kills with dual Glock 18s)
//lever shotgun bonuses
Kicks like a muel - 100 (15 kills with 1 Lever Shotgun)
short distance engagement - 250 (30 kills with 1 Lever Shotgun)
Shove it up their nose and pull the trigger - 1000 (50 kills with 1 Lever Shotgun)
//dual lever shotgun bonuses
Terminated - 100 (25 kills with dual Lever Shotguns)
Even better than a double barrel - 250 (50 kills with dual Lever Shotguns)
Hasta La Vista - 1000 (100 kills with dual Lever Shotguns)
//auto shogun bonuses
Buckshot artist - 100 (25 kills with the Auto Shotgun)
Scattergun master - 250 (50 kills with the Auto Shotgun)
Shotgun Sniper - 1000 (100 kills with the Auto Shotgun)
//rebound shotgun bonuses
On the rebound - 100 (25 kills with the Rebound Shotgun)
Can't miss - 250 (50 kills with the Rebound Shotgun)
Collateral damage - 1000 (100 kills with the Rebound Shotgun)
//pancor bonuses
No such thing as overkill - 100 (25 kills with the PANCOR Shotgun)
The more the merrier - 250 (50 kills with the PANCOR Shotgun)
Buckshot firestorm - 1000 (100 kills with the PANCOR Shotgun)
//spike grenade bonuses
Tactical Grenadier - 100 (25 kills with the Spike Grenade Launcher)
This is how to arc it - 250 (50 kills with the Spike Grenade Launcher)
Fire and shrapnel; this is my love - 1000 (100 kills with the Spike Grenade Launcher)
//grenade dart bonuses
Surprise inside! - 100 (25 kills with the Grenade Dart Launcher)
Five Second Fuse - 250 (50 kills with the Grenade Dart Launcher)
Tag! You're Dead! - 1000 (100 kills with the Grenade Dart Launcher)
//laser cannon bonuses
IMMA CHARGIN MAH LAZER - 100 (25 kills with the Laser Cannon)
IMMA FIRIN MAH LAZUR - 250 (50 kills with the Laser Cannon)
LAZOR OVURLOAD! - 1000 (100 kills with the Laser Cannon)
//tavor bonuses
This is my rifle - 100 (25 kills with the Tavor)
Bring on the assault - 250 (50 kills with the Tavor)
Never bring a pistol to a rifle fight - 1000 (100 kills with the Tavor)
//arrow gun bonuses
Skewered - 100 (25 kills with the Arrow Gun)
Human Shish Kebab - 250 (50 kills with the Arrow Gun)
Piercing Glare - 1000 (100 kills with the Arrow Gun)
//pipe bonuses
Crude but effective - 100 (25 kills with the Lead Pipe)
Clubby goodness - 250 (50 kills with the Lead Pipe)
Lead Pipe Ninja - 1000 (100 kills with the Lead Pipe)
//acid genade bonuses
Chemical Burn - 100 (25 kills with the Acid Grenade Launcher)
Flesh Melter - 250 (50 kills with the Acid Grenade Launcher)
Corrosive personality - 1000 (100 kills with the Acid Grenade Launcher)
Compare these with what you have in your Thing-Thing acheivement list. Once all of these is filled out, Artifact 19 is yours!
ENJOY!
oldlyshapedchris
Hey man i just looked at ur comix :O theyr awesome man
TacoRemix
heheh, dude those are nothin! i have a big book full of comics that i need to scan and put on my website. it has about half the entire pop-soda story panned out. its like 3 years work of random comics stuffed into this book.