I need a smile !

I'd say a good funny anime would be Daily Lives of High School Boys o gdgd Fairies. Both of them never fail to make me laugh.
Another anime I watch when I'm down is Tsuritama, which is seriously one of the best animes I have ever seen. It's really heartwarming and sweet, but is funny as well!
Also, maybe Axis Powers Hetalia? The episodes are only 5 minutos long and they're really funny, so I'd recommend it!

Try Fairy Tail

Nichijou and Watamote! are the only feel-good animes that I've really ever seen. Lucky estrella is good, too, but you've probably seen it. Nichijou packs a lot of laughs if tu just want to relax and not worry about drama o plot. Watamote! is definitely one of the funniest animes I've ever seen, so tu should really give it a shot.

Picture is from Watamote!!

Try Suzemiya haruhi yuuutsu

Special A

Cuticle Detective Inaba.

Here tu go dear!
hetalia
Tsuritama
Ouran High School Host Club
Nichijou
Usagi Drop
Shirokuma Cafe
Honey and Clover
Hyouka
Chi's Sweet inicial
Kimi to Boku

And that's all I can think of at the moment :)

K-ON
amor Live: School Idol Project (this really made me smile)
Sakamichi No Apollon
Ouran High School Host Club
One Piece
Usagi Drop

How about Prince of Tennis? It's really great and always make me smile! :)

Hadi girl - cute and funny.
Minami-ke (pic) - it always makes me laugh
Acchi Kocchi - it's also sweet and very funny.

One Piece

i have only 1 anime in mind that will change ur mood in noooo time..........One Piece

its the best........

im telling from my experience.........

this anime change my mind quickly
there were times i was down .......and sad......but then when i watch One Piece it made me laugh like crazy...and after some time......i think myself just few mins hace i was a sad person how did i changed my mood sooo quickly........
it happens especially when i see Luffy (the main character) comedy scenes.........he he he

One Piece is a great anime of joy, great adventure, great story line, treasure hunting, mysteries, action, comdy..........he he he
u will luv it for sure......he he he