I think that Percy's and Annabeth's song should be... I amor tu por Avril Lavigne :) If tu listen to the lyrics intently, You'll see how perfect the song is for PERCABETH~ :DDD
If tu listen too the lyrics the song says ' This amor is difficult but its a-real.' But for some reason i think its in Percy's POV because Annabeth would never be a complete rebel like in the song....idk it just seamed fitting. If i think of anymore songs i will add them too my answer por comment.
The Only Exception por Paramore: ESPECIALLY the glee version. Also I'd Lie por Taylor Swift, Stay Beautiful por Taylor Swift. Clarity (feat. Foxes) matches their situation in Mark of Athena perfectly. I completely agree with I amor tu por Avril Lavigne:)