A lot of things make me happy. The good parts of social interaction, food I like, being in peace and quiet when I want it, talking with someone you can confide in when you want social interaction.
The passage of time near the end of May, when it finally gets warm enough to walk around in summer attire. The sun, the nature, springing up from its withered winter depths, the hustle and bustle that inevitably shows up at that time.
Finishing a long project, or whatever, and seeing it received well. Coming out better than from something you expected to go bad. Or coming out of something really well enough, even if your expectations were pretty high in the first place.
Seeing something you've been waiting for finally show up. Could be anything. Could be something you've craved a lifetime, or something you've just developed a recent fascination with and liking to. Could be something material, could be something immaterial.
And before I go on rambling 'til the sun goes down, I'll also say that daydreaming makes me happy, at least for the duration that it lasts.
And thus, reading this post and thinking what makes me happy, and the things associated with those, also made me happy.