danm, everyone in the anime is a good choice. however, and this is a big one, look at the usefull/fun ratio they all have.
mostlikely you will comeout with either keyone, or reyoko, depending on how much you read or watch, or where you decide to stop.
now second choice will fall to mehoshi, ayake and washu.
now the hardest one is sasami, because she isnt grown up yet. now if you like loli, all the beter, but if she grows up into somthing nagging and abusive, kind of like everyones bad habbits into one