My favorite tracks would be:
1. Forest Temple (Very addicting music)
2. Song of Storms (Also addicting)
3. The music where you sneak into the castle (Even as a kid, I always loved this tune and trying to avoid the guards)
4. Zelda's Lullaby (Both the background music and the ocarina tune)
5. Spirit Temple (One of the few temples that has a memorable tune)
6. Saria's Song (Darunia's dancing just makes it better XD)
7. Zora's Domain theme (Goes perfectly with the water/aquatic theme, and it's catchy)
8. Gerudo's Fortress (What makes it so great is it's theme of "avoiding the guards")
9. Hyrule Field theme (Even though it's played a little too much in this game)
10. Kakariko Village theme (I know it's a blander tune than the rest, but something about it makes it catchier)
Yes, I made a Top 10 instead of a Top 5. But there are so many good OOT tunes, it's hard to pick just five. My last two listed is more of an honorable mention, but they're all good tunes nonetheless.