Marvel Heroes 2015
If you haven't played the PC game, Marvel Heroes 2015, you should try it. It has improved a lot since launch and you get to run around the Marvel U beating people up as Venom (or Toxin or Anti-Venom) for free! In their first ever SDCC panel, the team at Marvel Heroes announced some additional team-ups (characters that you can use to fight along side you for a brief period of time) including Agent Venom and Carnage:
Symbiote Rocket with Symbiote Groot was also announced as a playable character.
[Thanks to @OrionSTARB0Y for the tip]