This list does not include major multiplayer fps and most shouldn't be heavy-graphic'd. I have ruled out the local co-op games too 8,D

• Don't Starve Together
  
• Tabletop Simulator (check out the Workshop section for various board games!)
  
• Terraria
  
• Starbound (similar to Terraria)
  
• Crea (similar to above)
  
• Ultimate Chicken Horse
  
• Secrets of Grindea
  
• RWBY
  
• Brawlhalla (basically a free Brawl)
  
• BattleBlock Theater (mainly 2-player, but more people makes it PvP challenges)
  
• Magicka (recommended if you like Monty Python--trolly yet fun)
  
• Magicka 2 (sequel to above)
  
• Roguelands
  
• Moon Hunters
  
• Hero Siege
  
• Minimum
  
• NEStalgia
  
• Chaos Reborn
  
• Screencheat (ok, this is an fps but it seems amusing)
  
• Robot Roller-Derby Disco Dodgeball
  
• 100% Orange Juice (really cute, amusing, and fun online board game)
  
• 200% Mixed Juice (from the makers of above)
  
• Hammerwatch
  
• Dungeon Defenders
  
• Dungeon Defenders Eternity
  
• Dungeon Defenders II
  
• Orbital Gear (tends to go on-sale for $1, interesting game mechanics)
  
• Monaco
  
• It came from space, and ate our brains
  
• The Typing of The Dead: Overkill (first-person TYPING game against zombies)
  
• Fighties (fighting game)
  
• Mull Mojo Rampage
  
• SAMURAI WARRIORS 4-II (high graphics but seems interesting story-wise)
  
• Wanderlust Adventures
  
• Blade Symphony (swords....)
  
• Forge Quest (makes me think of Zelda)
  
• Hover : Revolt Of Gamers
  
• Marooners (seems similar to Mario Party)
  
• Holodrive (seems cute PvP)
  
• Broken Bots (seems dokily cute)
  
• Zombie Grinder (when you die, you get to play as a zombie!)
  
• Keep Talking and Nobody Explodes
  
• Kill to Collect
  
• Enter the Gungeon
  
• Dragomon Hunter (looks like a kawaii ver of Monster Hunter)
  
• Awesomenauts (limited to 3 players)
  
• Artemis Spaceship Bridge Simulator (game for the space-race dorks)
  
• Castle Crashers
  
• Orcs Must Die!
  
• Orcs Must Die! 2
  
• Broforce
  
• UnEpic
  
• Insanely Twisted Shadow Planet
  
• Metal Slug X
  
• Dungeonland
  
• Warframe (it's heavy-graphic'd due to workaround to be played on PS4)
  
• Trine
  
• Trine 2
  
• Trine 3
  
  
  
• Dead Realm (multiplayer horror--play as humans or the ghost--basically like tag)
  
• Damned (multiplayer horror--see above)