"A Song of Ice and Fire" from Game of Thrones. Doesn't match my theme but I'm obsessed with GoT and hearing the intro theme song makes me happy. Love that song.
I want the full version of that. Voyager's opening theme is my favorite theme out of all the Star Trek opening themes.
As for me, It's the beginning few notes of A Maiden's Illusionary Funeral ~ Necro Fantasy from Touhou's 7th game, Perfect Cherry Blossom, as it is Ran's theme, my favorite character of the series.