I discussed a case of this once on a different board, using D&D metaphors, but I think that it still works for d20 Modern.
Let's say that there are four players, and they are each trying to get into a nightclub. There are four doors to get in -- a North, South, East, and West door. Each door has an Incredibly Intimidating Doorman.
The Charismatic Hero tries to get past the Doorman at the North door. The Doorman tells him to get lost or get a good doctor. I roll Intimidate, the Charismatic Hero rolls his level check, and the results indicate that the Smart Hero is intimidated.
The Charismatic Hero says, "Okay, I apologize and start sucking up to him, telling him that I'm sorry I gave him any kind of trouble and making it clear that I'm no kind of threat. In fact, I wouldn't have tried anything if I'd known how tough this guy is. Maybe some sucking up through Diplomacy can get this guy's attitude good enough that I can maybe Bribe him or something. I'm scared, though, and if he doesn't bite at the diplomacy, I'm outta there with more apologizing."
I thank him for roleplaying.
The Fast Hero tries the same thing at the South door and is also intimidated successfully. He tells me, "Okay, in that case, I'm going to head across the street and hide in the shadows, then see if I can sneak in with a crowd. I'm scared to death of this dude, though, and if he gives any sign of having seen me, I'm making use of my good movement rate."
I thank him for roleplaying.
The Strong Hero tries the same thing at the West door and gets intimidated successfully. He tells me, "Alright, my guy's fists clench tightly and he shouts, 'Oh, really? You looking to start something?' Without waiting for a response, he attacks. He's freaked out and reacting with fight rather than flight, and I'm Power Attacking more than I should and Charging, even though I know that this guy is probably gonna hit me back."
I thank him for roleplaying.
The Dedicated Hero tries the same thing at the East door and gets intimidated successfully. He tells me, "Well, I'm going to ask him again and see if he looks like he might be up for a bribe. Does he look like someone I could take in a fight? Maybe I could sneak past him."
I tell the Dedicated Hero that his character is not ACTING intimidated -- those are all perfectly valid ways to act for certain character types, but he shouldn't min-max. He should decide what his character would do if his character were genuinely frightened that someone could do him grevious physical harm.
And if the Dedicated Hero insisted on trying to do other stuff, I'd start piling on circumstance penalties -- because the character is in denial about his own fear, everything that he does is affected by it.
-Tacky