-Seeing my child happy and enjoying things make me happy. I can just look at her facial expressions when we're doing something she likes and it makes me the happiest I can be.

-When I feel genuinely appreciated for something I've done

-Finishing a difficult task

-Seeing my friends (of which, there are very few) and loved ones with no real worries

Sexual things.

Eating KFC mmmmmmm

Nintendo.

Waking up right before my alarm clock goes off actually makes me feel unhappy. I'd rather have gotten 3-5 more minutes of sleep, but knowing the clock is imminent takes that away.

-Listening to music in my car on the way back from a day at work
-Video games (usually!)
-Good food
-TV of all kinds
-A really nice conversation (good friends, family, or the ladies)
-Cats
-Feeling appreciated (good catch, d21lewis)
-Finishing a major project of some kind (whether for fun, school, or work)

Music is one of my go to stress relievers and mood-boosters.
There is music for just about any emotion and occasion. It's great!

Other things make me happy of course, but that was the first thing that came to mind. A good book can also be very enjoyable. 

Also since I started exercising, eating better, etc, I'm much more satisfied and proud of my body, and that makes me happy! I like being sexy ;)

Sex, drugs, and rock 'n roll.

Just kidding.

Things that stimulate me mentally, but don't overwork me, if that makes sense.

I think that's why I like video games so much. They're mentally stimulating (more-so than a book or movie) but don't make you think too hard (unless you're playing a puzzle game or PvP game).

Having quiet time is nice. I'm introverted so being around people for too long grinds on me; it's nice to just sit down, relax, and think.

And Simple Man by Lynyrd Skynyrd always put me in a nice, reverential mood.
https://www.youtube.com/watch?v=4z3gkq_gWL4

Home-ownership and my girlfriend. Also Pizza Hut with extra cheese and stuffed crust with garlic dipping sauce. ;)

Nintendo and anime

-Threads like this! Anything that can make me think along radically different lines, open doors on new perspectives and draw comparisons between seemingly unconnected events or information. I'm probably most happy deep in thought and being creative.

-Alcohol, but this is not recommended if you're not currently not in a happy state of mind.

-The glorious feeling after intense physical exercise.

-A cup of coffee in the morning.

-Pulling off my work boots after a long days work, having a hot shower and getting into bed knowing ill have a long sleep.

If I'm not happy. I need a triumph. I figured this out years ago. You need something to fall back on in times of great stress, anxiety and even depression. The triumph can be anything, you simply need to set a goal, no matter how small, and accomplish it. It helps if it's something you can build on, but don't set yourself up for failure, make it manageable. If you have something in your life causing you great stress, you need to find a way out, or a viable means to thoroughly alter what is at the heart of the problem.

Trying new things also helps I've found. If you get stuck in a pattern or a rut, the monotony will take it's toll. Try something completely new. Cook a new meal you've never tried, read a book you normally wouldn't, go for a hike to a new place, anything, just break the pattern!