If you've got a lot of controllers and a lot of friends, these past couple years have been tailor-made for you. Between games like Towerfall (great), Samurai Gunn (great), Super Smash Bros for Wii U (okay), Divekick (bad), [also Gang Beasts and Sportsfriends, thanks Patrick!] and today's subject Nidhogg, couch multiplayer (also known as "min-esports," thanks Brad Shoemaker) is back in a really big way.
For my money, Nidhogg is your best bet. It's only 15 dollars, there's online multiplayer, and the core is so engaging that anybody could easily pick it up and have a good time. That describes a lot of these new local multiplayer indies, to be fair, but Nidhogg is so tightly crafted that it makes everything else look foolish in comparison.