Iron Man might find a use for this Tech card because it adds to his hand size in hero mode, and once it is spent it can be returned from the discard pile using Stark Tower. This is nothing new for Tony; he was already doing this in protection with Energy Barrier and Electrostatic Armor, and in leadership with Power Gloves and Reinforced Suit. Yet being able to build his hand quicker in aggression opens up some interesting options to turn him into a pretty fierce basic attacker, thanks to Arc Reactor, Combat Training, Bug, and possibly Earth's Mightiest Heroes with some of the decent red avenger allies. It doesn't even clash with another weapon because he doesn't have any other hand-held / restricted items in his kit!
Another hero to really make good use of Hand Cannon is Quicksilver, for many of the same reasons with the multiple attacks per round to pile on the damage, and the lack of a clashing weapon.
Thor, Black Panther, Captain America, and Hawkeye all prefer Jarnbjorn. The real question is which weapons are going to find a home in Agent Venom...