Vita, without a doubt. All dat Nep-Nep.*_*
3DS is a close second. It has an amazing library as well.

GBA.

PSP was also very awesome but it didn't have Golden Sun and Lost Age.

PSP because of Pon Pon Pata Pon! this game made me put down my DS

GBA, so many good times I had with my SP. From Pokemon, Mario Superstar Saga, Metroid, Battle Network, I loved that thing. Really the platform which introduced me to a lot of Nintendo franchises.

right now for me its the 3DS

might change to GBA after i beat Mother 3 tho

3DS for sure. Just so damn many great games, and I love a lot of the features.

Gameboy Micro so neat and compact! Closely followed by the Vita. There is no competition on the current market.

Strangly Psvita, but just because i have so many rpg to enjoy on this !

PSP i like to play most succesfull Playstation games on handheld

To be honest, I don't have a favorite handheld. I've been playing handheld games since getting the Game Boy Color. I've owned every single Nintendo handheld from GBC onwards. Although I like Nintendo's handhelds, I'm open to playing games on other handhelds. That is why I decided to go for the PS Vita (my first PlayStation system). Looking forward to playing games I have missed out on like God of War and Sly Cooper.