After reading Katawa Shoujo.
After finishing Dragonball Z.
After beating Crysis 2.
After beating any hard game that pumps your adrenaline ever.
After finishing the last percy jackson and the olympians book.
The feeling of emptiness. Fuck.
I finished a book, titled Exit Here., and I felt so empty not having it in my hands I read it again.
I'm not much of a gamer, so I don't have much I can mention in terms of games, but there are a few series I really like... Zelda is one of them. Twilight Princess... second-to-last dungeon left me exhausted, final dungeon wasn't as great but by the time I finished it all? The ending was downright epic and it had me just sitting in front of my Wii staring at the screen for like a full minute after the credits completely stopped.
There were several other Zelda games that were similarly awesome, but Twilight Princess was the best in my opinion and instilled this feeling better than any other.
After finishing a good book or movie or video game, I stop and think, "What the fuck am I doing with my life?"
Then I go on the internet.
And I suspect I will get this feeling after reading all the books in the Dresden Files series by Jim Butcher.