Splatoon is an upcoming third-person arena shooter developed by Nintendo for the Wii U. It's due to release in Spring 2015.
You fight using paint guns on one of two sides, and the goal of the match is to paint the floor of the arena in your team's color.
You move at a normal speed when walking over your paint, but you slow to a crawl when walking over the enemy's color. And if you get covered in too much of your enemy's paint, you'll die and respawn back at your base. While on your own color, you can also sink down into the paint to ambush enemies or to swim between pools of paint at high speed to rush around the arena.
Oh, and you're playing as some kind of anthropomorphized squid girl.
Here's the E3 announcement trailer:
It looks like there's a variety of weapons available, as well as cosmetic customizations for your characters. And while the game is focused on online multiplayer, there's a single player campaign, as well.
This isn't quite Nintendo's first foray into online multiplayer shooter games, but it's their first for a home console. It looks like it brings a lot of creativity in both visual presentation and design, and I'm super excited to play it.