Path of Exile, it's like Diablo but it's more complex and has more things to do.
Edit. It has micro transactions but they are purely cosmetical. (ok there are some that are for your stash but you can live without them :-P)
Edit2: Yeah, Hearthstone too! Because of cards and how it's made :)

Heroes of the Storm, Rift, Airmech, Trove, Hearthstone, Minion Masters, and Ghost in the Shell First Assault Recon were not even mentioned in that poll. =(

Reason why I like Heroes of the Storm, is because I have always loved/enjoyed the Blizzard Characters in Defense of the Ancients back when it was a mod of Warcraft III Reigns of Chaos.

Should also note that my favorite parts that I play in Starcraft II (coop commanders), is free to play for those with just the Starter Edition (you get Raynor, Kerrigan, and Artanis for commanders).

Nothing from the poll list
oh wait, I'm playing f2p game on my phone

Quake Champions

magikarp jump.

Paladins <3

Guild Wars 2 is the best / testing graphic http://www.kingrpg.net/2015/03/guild-wars-2-gemfx-realistic.html

HearthStone and Alien Swarm reactive drop.

I have thousands of hours on Neverwinter and Star Trek Online. They are kind of P2W, but if you don't do PVP you won't notice. They also give top prizes to everyone participating in their 3 yearly events (summer, winter and anniversary) so you won't be stuck with crappy stuff for long. You can also buy almost everything from the store with an ingame currency (you can trade it for "premium" currency), it's grindy but it works (somewhat better in Neverwinter than in STO).

Been playing Planetside 2 since it first went public years ago. Great game despite it's many faults.

I guess its league of legends. 😒

View attached image.

Hearthstone

There's several I enjoy.. Marvel Heroes Omega, The Elder Scroll Legends, Hearthstone, and Brawlhalla. I could say Pinball FX2 cause the base Pinball table is F2p but I mainly play the DLC tables.

It's hard to choose between Unturned and paladins. I took Unturned because I had so many moments of pure pleasure but it's been a few months that updates harm the game. Paladins is a really great FPS/MOBA game and is the best game in the list to have fun with a good gameplay.
I see some people talking about Path of Exile, I'm playing this game too but it's not that great, it's a little boring and the first 3 acts are so easy that you never need to heal.
Edit : I use to play brawlhalla when it was the beta but the game still have lag problems and new characters are quite uninteresting

Dirty Bomb is great. Though a rant by AngryJoe made the game feel like its P2W by many people but it clearly isn't.

Eternal Crusade mostly because of WH40K setting i guess. But its decent game in its own right. Especially considering problems it had.

I have a couple of favorites, Warframe and League of Legends. While I don't play either anymore, they are both great games. I simply played way too many hours in both and got burned out. Neither game is Pay to Win, their payments are either cosmetic or to cut down playtime to get what you want faster. That to me seems like a waste though, why pay to skip content? If you are one of those that must get everything then I think both games are not for you unless you want to pay heavily. In either game you can fairly easily flesh out your arsenal to a reasonable degree and just play the game and have fun. As you play you will unlock even more and, again, just have fun. Warframe has the advantage that you can trade items you get in game with others for premium currency that you can then use to unlock more gear slots (admittedly low to start with) and all the cosmetics you want. Heroes of the Storm is a fair alternative to League of Legends, its a lot more friendly to newer entrants but not one of my favorites unlike some of my friends who enjoy it more.

Awesomenauts
Wasn't always F2p but went recently.
I have hundreds of hours in this game and really enjoy the mix of platformer and moba.
The developers release regularly new patches with new features, characters and more.
I really love it and it's my most played game of all time :)

I played a lot of Dirty Bomb before. I think I almost or already clocked in over 100 hours of playtime. If you like shooters, give this one a try.

Marvel Heroes Omega is my favorite F2P game and it has a fair F2P model. And i enjoyed TF2 so much too. :)

Paladins is fun. Crossout, Path of Exile, Warframe, Forge of Gods are also pretty good.

i suppose it's league of legends but i stopped playing it long ago.

alien swarm was also amazing.

Mine is Fallout Shelter XD