Gem Craft - easily one of the finest, if not THE finest, tower defence game series. Great concept, simple yet pleasing visuals and hard as diamond gameplay (ou know, as in gem, ha ha- no? oh...). I've never managed to complete any of them, there's always a boss that manages to beat me by so little, and I refuse to use a strategy guide. One day I'll conquer them, one day...
I have recently discovered krew.io You are on a boat as either the captain, or a crewman on someone else's boat, and the goal is to eat supplies and bully other boats.
Treasure Arena! The sequel one is available on Steam. (Super Treasure Arena) It's a multiplayer battle arena game that has similar combat to Enter the Gungeon. Rolls, Shielding, different weapons etc. Nowadays, no one is online to play it.
I have quite a few to add, but some of the ones that came to mind were: http://incredibots.com/ http://fantasticcontraption.com/original/ http://dan-ball.jp/en/javagame/dust/ Also Bubble Tanks 2 and 3. I remembered about some poly spaceship building game for free which was really really cool but I forgot the name. And there was some game on Kongregate, something about cards and that you had to swipe them all away before the screen moved to another view. Also some battle with the card king. I forgot the name though and I really want to play it again because it was so damn fun, but I haven't been able to find it.
Highgroundsgame.com It's kinda like Magic the gathering, but not. Well... It's an online card game, but instead of cards, it's units. There aren't spells, and cards have 2 triggers. Front row and Back row. Placing your units in the front or back makes them have different effects. It's like my break from Hearthstone.
This thread is bad for my productivity. I like the Zombotron series, there's three of them now I think. Just a standard platforming / shoot-em-up game with zombies and robots. teammadness.tumblr.com