Hugging my daughter and giving her kisses on her neck until she giggles.
Usually works for me…
I usually go for a drive 30mins to an hour and listen to my ipod, maybe either angry late 90s nu-metal from my teenage years, or just a good blend of classic rock and roll sorta things. Or if I am bummed and WANT to be happy- my Steve Miller’s Greatest Hits CD. If the drive isn’t looking like it’s working- I go off and read comic books in public, maybe browse for CDs (closest thing to shopping for Guys, next to “searching” (aka just browsing) for video games imho). In college, I’d go and see a movie with friends or something- basically when I knew I wanted to be alone and sucky and pouty- I forced myself to interact with people but in small controlled doses to get over it.
Sitting around the house moping never really did it for me, it just worsened my feelings, hence the getting out in various ways sorta thing.
Running on a trail in the woods always seems to lighten my mood…that or alcohol, your choice.
It usually means I’m hungry.
Maybe you need a different Video to watch. The last time I was in a bad mood / funk, I watched the movie Grumpy Old Men. Fixed me right up. My wife told me it was nice to hear me laugh again.
Show tunes!
Note: do not do this if the milk jug is made of glass. 
I second (third? fourth?) exercise; yoga works for me, as does taking ten or so deep breaths.
If I’m somewhere where that’s not an option, I give myself a time limit (5 mins or so) and REALLY let myself stew-just wallow in self pity and rage for a couple minutes and think about everything that’s wronged me in the most ludicrous terms imaginable. By then it either goes away or is much lessened.