I think the most fun, yet annoying, use of Talent Law I've made is "Split Personality". We tinkered with the rationale, but it worked the same in practice. I'll try to keep this short (not all the back story)
Twin brothers, one a Warrior Monk the other a Mage, were abducted by a villain. A spell/curse was placed on them so he could use them as henchmen, but he was only able to control one at a time. So, the villain set it up so he could instantly swap them out wherever they are. The one currently not being controlled would have no idea that he was doing anything other than what the twin had just been doing, just in his own way. Being a character with a robe and a staff it was the perfect 'cover' so-to-speak.
So, in the middle of a fight the Mage twin casts a Firebolt and the next round is switched and makes multiple melee attacks with his quarterstaff. One of the other players was going nuts because he couldn't figure out how I was doing those things with the same character. He'd say "But you just firebolted that guy!" and I'd say (cause I had to roleplay it) "No I didn't I hit him with my staff." I'd also 'mysteriously' not have any wounds after I'd obviously been hit (i.e. the twins swapped and the other was fine). That player actually got slightly annoyed at one point cause I was always evasive about it. Not sure if he thought I was just screwing with him or what. He partially finally figured it out when the players finally realized I said I was a Warrior Monk at one point, then later claimed I was a Mage and both reference their twin brother who needed to be save that was the opposite profession (course they partially assumed it was the "Split Personality"). Course, then we confronted the villain and we had the cliche "fight with the evil twin" battle.
I have to say, while it was fun, it could be really annoying at times. At least when I was flying as a Mage and the twins swapped the Warrior Monk one was almost always able to mitigate the fall with the moving maneuver skills he had. Not sure I'd want to do that again though.