LOL Lurkerprime at your comment I do play a lot of xin, but he's my favorite for a reason as I just think he has a lot of versatility and balance to him. He works well for any team and just takes switching a few items in his build to counter most heroes.
Another hero not mentioned earlier is Gragas. Who is free this week. I always thought he was good, but man that guy is way more OP than I previously thought before. I went mid against him as Xin and we were doing a lot of simultaneous deaths. And neither one of us were being stupid. He just puts out ridiculous damage at low levels with that barrel of his. It dishes out a ton of damage, it's AoE, and it takes very little mana. He has a teleport on demand dash to initiate or escape (and go through walls), a low cooldown self heal, and a really nasty ultimate. He's also technically considered a tank which means his base stats make him hard to kill even without any tank items (like Garen). I recommend people try him out now while he's free.
Personally, I got to finally try out Sona last night. My friend's daughter plays her often and she does alright with the char from what I've seen. Still I wanted to give the char a go. I'm not usually big on playing support chars in this game though. Why? Well the reason is because I have to rely more so on my team mates as support char to know what they are doing to win. Still, I thought I'd give it a go. Basically as long as I'm on a team with people that aren't complete dipshits, a well played Sona will turn even average players in team fights into gods! After several games last night, I need to show my friends daughter a bit how to play her, but not sure she'll pick up on everything though. Still have to try. For those wondering around here as to what I did with Sona, here it is.
First, off my runes. I have a caster dedicated rune page done as the following:
Marks - Magic Penetration
Seals - Magic Regen/5 sec per level (+0.1 regen per level)
Glyphs - flat cooldown reduction
Quints - Health
For my masteries I went with:
Assault (9): 3 in ability power, 1 in crit chance, 4 in cdr, 1 in magic pen
Defense (13): 3 in magic resistance, 3 in armor, 4 in dodge, 1 in nimbleness, 1 in hardness, 1 in scars of veteran
Utility (8): 3 in regen, 1 in ghost, 4 in experience gain
I take Clarity and Ghost for summoner spells.
I built her items in the following order.
First I picked up mana manipulator. It gives a nice 7.2/5 sec mana regen to Sona and all allies around her. It costs 475 to make so there is no more money left over for anything else at the start. Next I buy a catalyst and use that to complete an Innervating Locket. Then I buy tier 1 boots. Then I buy another catalyst and use that to complete a rod of ages. Now I complete my tier 2 boots as either merc treads or sorc boots or swift boots (all three work well for Sona). Then I got for an Arch Angels Staff and then Zhonya's ring if the game has managed to go on that long. I didn't ever get to complete Zhonya's Ring let another anything else after that or I would have gone for another Arch Angel staff.
For skills I went in this order:
Q, W, E, W, W, R, E, W
I prioritized my Healing ability (W) first. I took my Ult every level it was available (6, 11, 16) and only built up my Q last. Cause face it, I'm there for support not damage.
With the Rod of Ages, Arch Angel Staff, and Innervating Locket I had just over 3K hp's at level 18, 3600+ mana, 300+ AP, and was damn impossible to kill. If I pop Ghost and Sona's speed ability I was zooming around at 600+ speed. If the other team tried to focus me, I was healing for about 500 a pop + my massive aura regen and moving really fast so I was hard to catch. Which means my team was able to beat down upon anyone stupid enough to try to come after me. Let alone Sona can still stun for a getaway if needed.
Basically I was playing heal and buff bot for my team while being a not so squishie target. My damage output was okay, if nothing nearing my Xin build, but I made everyone else on my team deal more damage, regen health and mana, run faster, attack faster, and have more armor/MR. I basically have unlimited health and mana with this build. What I lack for in damage output in a team fight, I more than make up for in other ways.
Sona's glaring weakness is how squishie she is at low levels though and her need for mana to do anything. Low levels the mana drain is bad. Also, she doesn't farm well. She's actually pretty bad at farming. Sona must rely on assists for gold from her teammates. Which means in order for Sona to do really well in a game, the rest of the team can't be complete idiots. If they aren't Sona can make a good team into an impossible to beat team. However, if the team is complete idiots, then Sona isn't going to be able to do anything on her own. Which is another reason I typically play Xin, cause if I can get Xin built properly for the late game, Xin CAN win games by himself just about. Sona will never be able to. Still if you have some friends to group with that you know are at least decent players and you like playing support, you can't go wrong with a Sona built like mine.
Some other tips for playing Sona. Don't be afraid to use your abilities as often as you can. Healing + Speed for all teammates nearby is crazy good. Learn when to use that Ult of hers. Never for one second think you can solo ANY enemy hero that is at full life. Do not chase. Do not initiate the fights. Learn to move around during team fights between team mates to make sure everyone is getting healed and receiving buffs if at all possible.