Hmm well there's a lot of them I guess.
Some of them are:
Namie Amuro - WoWa
- I was listening to this when I was so happy because my father ordered my first ayu album (GUILTY). Even when I listen to it now I remember the EXACT happiness I felt at that time and it makes me feel awesome all over again
alan - Natsukashii Mirai ~longing future~
- Because it gives me chills down my spine every time I listen to it and makes me incredibly touched in heart.
melody. - Lovin' U
- Like someone said about this song before, it's all about feeling good
melody. - Say Hello
- Always makes me feel happy.
Perfume - ONE ROOM DISCO
- This is the only song I like by them, and it really makes me feel incredibly great.
sifow - LOVE & PEACE
- This one is veery cheerful!
Nana Tanimura - every-body
- It never fails to make me feel amazing.
And many more.
EDIT: I forgot to mention the most important song, Namie's CAN YOU CELEBRATE?. That one is always to make me feel nostalgic and simply great.