I main Sona and Janna as support. Honestly, I find that Janna goes better with some ADCs than others, and I only really play her as a counter pick to Blitz, Thresh, or Leona (the disengage is real).
(However, I must defend Janna since she is a support goddess. She most certainly does not fall throughout the game, and so long as she is alive she is beneficial to her team providing passive movement speed boosts and having two disengage abilities (Q and ult) and a damaging slow (W). She is most effective using her Q during a team fight to turn it into your teams favor or using her ult to push the enemy where you want them to be--either towards your team or away--and gives a pretty decent heal to bring your teammates back into the game rather than them retreating. She's a great team asset)
Almost every other time I go Sona. Both are utility supports, but Sona also hurts. A lot. So if you're looking for a utility based support that can be aggressive, Sona is a good pick (as is Nami or Lulu).
Lately I've started playing Lux and Morgana a bit more. If you're good at skill shots, their Qs can be very annoying to the enemy (that 3 second Morgana Q, ugh). Other skill shot supports that can pay off are Blitzcrank and Thresh, though I honestly don't play them.
Then there's always Ashe support if you're feeling ballsy.
