1. Clannad (1st OP: Megumeru) - Love this one because 1) the show evokes such an insane amount of emotion that it's impossible not to love this opening, 2) I adore the song, and 3) the amount of foreshadowing, even to events in the second season of the show, is astronomical. Clannad is guaranteed to make you fall in love with the characters, and will probably make you cry at least once, no matter how tough you are.
2. Death Note (1st OP: The WORLD) - Because of the sheer amount of symbolism contained in it, and just for having an awesome song that got my blood pumping before every episode.
3. Naruto Shippuuden (Blue Bird) - Because the show is always packed with emotion, so the songs often bear and reflect that. This amazing song is no exception, with one of the series' better opening videos to accompany it.
And... screw it, I have to include them!!!
4. Full Metal Alchemist (1st OP: Melissa) - Just... great song. And the video is fantastic, pairing perfectly with the early events of the show.
5. Darker Than Black: Gemini of the Meteor (Tsukiakari no Michishirube) - Great song, great video. I really don't know what else to say. Watch Darker Than Black, then partake in this excellent sequel season.
6. Digimon Tamers (The Biggest Dreamer) - Same reasons. Love the song, love the video, foreshadowing is fantastic, etc. Amazing show: it was season 3 of Digimon.
I know I went way over 3, but I couldn't bear only listing three of these... and I even left out Haruka Kanata and Tori no Uta...
