The Stoat & Bear wonder....

[Gemini Cricket]

Lots of songs make me happy. The list is huge and changes all the time. But in answer to the OP's question, I'll go one step further.
I'll tell you and show you.

Sunchyme ~ Dario G

Slow (Chemical Brothers Remix) ~ Kylie Minogue *

Love Will Never Do (Without You) ~ Janet Jackson

These three always, always cheers my sad ass up when I'm gloomy.

A runner up is:

Tears Dry On Their Own

Even though the words say it's a sad song, the music lifts my spirits.

The following are ones I love, too.

Originally Posted by lashbear

Bear's:
Make Your Own Kind Of Music by Mama Cass Elliot

Originally Posted by Chernabog

Wig in a Box (from the Hedwig and the Angry Inch

Originally Posted by LSPoorEeyorick

If You Want to Sing Out, Sing Out - Cat Stevens
19-2000 - Gorillaz
Ana Ng - They Might Be Giants
Ballad of John and Yoko - The Beatles
For Now - from the musical Avenue Q
A Little Priest - from the musical Sweeney Todd

*This one was not chosen to butter up the Australian OP's.