My "rain" is older than most, I fear.
1. Weathergirls' "It's Raining Men"
2. Ex-Spice Girl Remake of #1 (used in Bridget Jones' Diary)
3. Raindrops Keep Falling on My Head
4. Prince's Purple Rain
5. Stormy Weather
6. Lena Horne's rendition of "Misty"
7. "Don't Rain on My Parade"
8. "Dancing in the Rain" (the 40s Broadway version)
9. the Broadway "Rain man"
10. Broadway: Aquarius/Don't let the sun shine (from Hair)
11. Fifth Dimension remake of #11.
12. Shostakovitch's symphonic etude
13. Debussy's "Rain"
14. "When it's raining"
15. "Into each life, a little rain must fall"
16. "Golden Showers," soundtrack to 1970s Johnny Holmes' adult video
17. Broadway: "Rainmaker"
18. The Carpenters' "Rainy Days and Mondays"
19. Classical Chinese piece: "Rain"
20. Japanese pop song: "Ame ga futte'ru yo"
Ouch, and those are just off the top of my head.