It would beeeeeee . . .
supercell's 'Koi wa Sensou', 'Hajimete no Koi ga Owaru Toki' and 'Kimi no Shiranai Monogatari'
Tada Aoi's 'Brave Song'
Hatsune Miku's 'crack' (unsure of producer)
Lia's 'My Soul, Your Beats', 'Kizunairo', 'Doll', 'Tori no Uta' and 'Toki wo Kizamu Uta'. Heck, just about anything by Lia, though those are my favourites, in order. The girl has the most beautiful voice I have ever heard.
I also like m.o.v.e.'s 'Super Sonic Dance' and Miyavi's 'Selfish Love'. Not quite epic enough to have their own lines, though.