Probably the best online game ever.
Made by Jim Bonacci (and some done by Jason Schymick), who also made the (less known) game Divine Intervention.
As described by Jim himself, the goal of Happy Wheels is "personal victory at any expense". And that's exactly what it is; you ride on a vehicle and your goal is to get to the finish. You can lose all your limbs, your son, your own vehicle, as long as you make it to the finish alive.
It's free, just go to the site and you can play it. It's on totaljerkface.com
However, there are way too many copied and unoriginal levels, like: Rope Swings, Kill Justin Bieber, Fight Chuck Norris, Ragdoll (also known as "fall down"), Jet Fall, Weapon Throw, "Rate 5 too see random glitch", Glass Fall, WWE, Saw: The Game, Arrow/Harpoon Run, Zombie Kill, Don't Move/Heart Donation, HOT FREE SEX, and the recently invented: "Made for UberHaxorNova".
It's recommended to not play these at all, and if you accidently click on one, you should rate 0.
It gets uploaded once per one or two months.
The only thing that will prevend you from playing it, is Headache Puppy, because he does not approve of repetitive refreshing.
Guy 1: Hey dude have you seen the new featured level?
Guy 2: Yeah it's way better than all the Kill JB's.
Dude 1: Hey are you making your homework?
Dude 2: No I'm playing Happy Wheels.
Person 1: Hey.
Person 2: OH MY GOD HAPPY WHEELS IS UPDATED!!11!