I'd be a boss for an action game. Extremely quick and using daggers, throwing knives and smoke / flash bombs.
My strength would lie in my speed and maneuverability so that I could get close to the player and unleash a flurry of attacks while dodging any counter attacks. If an opponent tried to keep me at range I would unleash volleys of poisoned daggers to stun / cripple them as I close the distance.
At about half health I would then throw a handful of smokebombs covering the arena in a shroud of dense, grey smoke. Causing visibility issues for the player. It is then that my strategy would change and I would use my stealth to launch opportune attacks and flashbombs to temporarily blind my opponent so I could retreat back into the smoke. Sometimes launching volleys of daggers from the fringes of player vision just to disappear again as they attempt to dodge the attack.
At 15-20% life the smoke shroud would lift and I would get an adrenaline rush, increasing my speed immensely. I would follow the same attacks as my first stage but slightly more reckless and erratic.
As the swing that would finish me is launched I'd parry with a dagger and launch a final flashbomb to cover my retreat. On the ground after the battle the character would find the same daggers I was using, which upon equipping would bestow them with the same speed I had fought with.
My weaknesses would be my vulnerability to physical effects, such as slowing my speed down. It would severely hamper my combat style though I would become more resistant to it if repeated uses were attempted. Also I would be wearing a lighter more flexible armour, meaning strikes that connected would connect with near the full force that was intended. The final nail in my inevitable coffin would be my mediocre health pool. Not terrible, but not too great either.