"Gotcha" powers basically. Boring tanks give their enemy no good options and no openings. Fun tanks create new incentives. Tricky tanks would make opponents think it's in their best interest to attack them when it actually isn't, which is the deception I'm talking about.

Literal illusions and deceptions would work, but so would someone who seems to be the path of least resistance until gotcha effects turn the situation into one the attacker wasn't expecting. Maybe they seem weak but have a lot of contingencies, or maybe they seem very threatening when they're actually fangless with mainly defensive powers. Either way, to be a real tank, the key part is how they thrust themselves into the situation instead of being just a distraction on the side.