It has to be Fortnite for me. The game is free and was just something people didn't even care for at one point when it came out. And now look at it, it's making millions every day and it is known globally. It helps that the developers care about us and actually listen to feedback that we give to them on Reddit and Twitter. You can see how far it has come considering the first ever virtual concert occurred in Fortnite yesterday!
I guess hungry shark was one of my best favorite free games to play because of its very exciting and fantastic gaming experience that it will give to us. It was really very addictive since sometimes I am devoting my precious time in playing such games because the level of difficulty is really challenging that you will really try your best to accomplish certain goals from the game and I really recommend this type of games to everyone out there since it is full of fun and excitement.
Every game is a free-to-play game where I come from ? Joking aside, my personal best, the one I am still playing, is League of Legends. I don't have much time to spend on games nowadays, so it is perfect for me, the game is from 20 to 40 minutes long, there is no preparation for it, and you don't have to think about it afterward. Graphics and mechanics are great. All my buddies are also playing, so we make our own team of 5 and play together from time to time.
I think if you are on Steam then you can find plenty of news on the free to play games. In case of Android, you have to check the playstore for the free to play games. I find most of the humble bundle games not that exciting for playing the new games. Most of the indie games there are boring. So I prefer something better.
Team Fortress 2 is a great free to play video game. It's a shooting game which requires a lot of skills and time to master but once you get how the things are working it will be easier. Dota 2 is also good if you like MOBA. Now that CS:GO is also free you can try it too but be prepared to meet at least 1 cheater in every 2 competitive games. There are a lot of cheaters and griefers in Prime and what's left for the Non-Prime side... You get a free Prime status once you reach level 21, which doesn't take a lot of time.