2. Opportunity Attack does not trigger Aegis of Fame -- it skips right to the dice and resolving.
I think I need to ask an in-depth question about this answer.
Aegis of Fame says "An enemy gladiator model must spend 1 Favor to attack this model."
Note that it does not say "to declare an attack". It just says "to attack".
We know that declaring attacks has certain rules and restrictions about it. But simply "attacking", without a declaration, is something else. For example, Taunt and Fade prevents you from declaring attacks against certain models. But it doesn't prevent just attacking those models. Spite is an example of an attack that doesn't declare. So Spite would ignore Taunt and Fade.
So why exactly is it that neither Opportunity Attack nor Counterattack trigger Aegis of Fame?
Neither of them declare attacks. They both declare reactions, and the rules for neither of them mention anything about declaring attacks. But Aegis of Fame doesn't require you to declare an attack. It just requires you to attack.
I have a hard time imagining that making an opportunity attack doesn't count as attacking. If it didn't, then Ywain's Rebuff wouldn't work against it, Envenom wouldn't work with it, just as a few examples.
The reason I thought of this is because Stheno has her Inevitable ability that works when she makes attacks, and it seems like she has a special Desultory rule that prevents her from making counterattacks, because otherwise Inevitable would work with counterattacks, and that would be too strong. This suggests that counterattacking counts as attacking. Which makes intuitive sense to me. Attacking means rolling your attack dice.
So as I see it, as the rules are written, Aegis of Fame works against both opportunity attacks, counterattacks, and Spite attacks. But it's not meant to. But if you say that it doesn't, without changing any current rules, then logically, lots of other things stop working the way they should.
Trying to guess intent, it seems to me like Aegis of Fame is actually meant to say "An enemy gladiator model must spend 1 Favor to declare an attack against this model."
Then you can say that both counterattacking and opportunity attacking counts as attacking, but not as declaring attacks, and then everything seems to work in what seems to be the intended fashion as far as I can tell.