Political Assassin
I guess the term "political assassin" is misleading. I'm looking for a cohort to basically work as the King's bodyguard, assassin and generally menacing character. A political assassination could be just bullying someone into dropping their cause, trick them into doing something else, or kill them as a last resort.
The assassin class would work, I just think the spell list is horribly limiting and would like something more flexible or useful. That said the death attack ability would be very nice to have, does any other class get that? I looked at Shadowdancer and I may do it, but the shadows seem very weak compared to the character.
Since the character that is picking up the cohort is a monster class, another monster would work our well. I was thinking of using a doppleganger with the prestige class that let them use their mental powers as a free action to improve their combat ability, but the people on enworld are really creative and usually come up with something really unique that doesn't suck (read powerful.....this game is bordering on broken so it has to be powergamed a bit).