If your character is so badass that such showmanship is not needed, because you can take people down with one swipe anyway, then its a case of poor game balance or maybe game-table intimidation rather than in-game intimidation. Besides, role-playing a low-Cha character with too much attitude really is to step out of character.
WHen the PC started, he had an 8 CHA, by the time he was done, he got to 10 or 11 (I did some stuff to improve CHA).
Whether we were out of character or not is a tough one. I played him as the big guy who knew he always got what he wanted, but seldom spoke. Like all half-orc barbarians, his INT was also not stellar. I just happened to not have totally bad modifiers on those stats, and I had a pretty high wisdom. So I played him as somebody who didn't do dumb things, but also wasn't the guy proposing plans, particularly complex ones.
His most complex emotion was regret as in "I knew I should have killed that #%$#$%#^%$ gnome instead of let you fools talk to him!"
He wasn't clumsy, he wasn't dumb, he wasn't badly mispoken or socially awkward. Particularly in a frozen tundra setting where darn near everybody is a barbarian and the core PH races are exceptions rather than the rule for societal norms.
Anyway, the core point of talking about my character was really to illustrate the silliness of the Intimidate skill. Where I had a PC built to be physically intimidating. The DM and other PCs were intimidated, the fluff said I was intimidating. The dice rolls, not so much. And part of it was just bad rolling.
Granted, if it did work a lot, my character would get the new emotional scene of "Come back and fight me!" a lot.
My main beef with the skill was that it was a class skill. I actually took ranks in it, and it was NEVER useful. Given that there wasn't a critter in the MM that I needed to be scared of (from his perspective), I took ranks in it because it made sense from a role play sense (he was intimidating, back it up with points in the skill). Its simply that the game mechanics failed to deliver on what I payed for. Granted, pretty much all the skills a barbarian gets suck...