RocketBirds on Vita is darned good fun. Laugh-out-loud fun, in fact. Wow I love this game.
Also, Let's Fish! Hooked On is all kinds of addictive fun.
That's what I love about the Vita so much. Look beyond the fact that it has limited AAA-games, and there's a real wealth of smaller stuff that is so much fun to play. I love this console.