Neil Gaiman's graphic novel series The Sandman has several Norse mythology-inspired characters, including the trickster Loki.
In the movie The Mask, Jim Carrey's character gets into all sorts of trouble when he puts on a mask of Loki's face.
Neil Gaiman didn't leave Loki alone after The Sandman. In 2001 he wrote the novel American Gods, which includes Loki (under the name Low-Key Lyesmith) as a character.
LOKI is a PC video game that gamespot.com calls "a solid rip-off" of Diablo II.
In Too Human, an Xbox 360 game, you get to play Balder (called Baldur) and fight against Loki and his army of machines.
The movie Thor is based on the Marvel comic books, and you know what that means: Loki is a total villain.
This animated motion comic from Marvel seems to have a less black-and-white take on Loki: "But just why does Loki hate his brother Thor? And could it be that this master of mischief isn’t really the villain he’s been branded? Loki's insatiable lust for power and his feud with Thor take on new meaning in this resonant epic."