Recently, I found this Nico Nico Douga singer going by the name of Nayuta. Her style is that she tends to injects feelings and emotions into the songs she covers.
First up, we'll have a song that all Miku fans and Ryo fans will know:
Hajimete no Koi ga Owaru Toki - Hatsune Miku
Other songs covered by her include the following:
[SuperAnimeRemix]God knows... - Suzumiya Haruhi no Yuuutsu
I thought this was really Hirano Aya singing and talking. Nayuta is THAT good.
Romeo and Cinderella - Hatsune Miku
Her voice here sounds strained but no matter, it still sounds nice :D
Black Rock Shooter - Hatsune Miku
You - Higurashi no Naku Koro ni
Nico Nico Douga song (i forgot the name)
They use the same songs as the original but the lyrics are different
unknown girl - Touhou
One of Flandre's themes