Bleached white skin (perma-white), wears lipstick to make his lips red. His hair was also bleached in the accident (more realistic than having it dyed green, imo) and so dyes his hair green.
Joker venom is a chemical weapon that initially reacts like laughing gas, but is ramped up to the point of suffocating the victim (can't breathe if you can't stop laughing) and finally stretches the facial muscles into the trademark grin.
Other weapons at Joker's disposal are knives, a machine gun and a custom joy buzzer he modified himself.
I imagine a Joker with an engineering background who can create chemicals and different weapons. Not really a fighter, but not a complete wimp either.
There, a realistic take on the classic comic Joker. No smudgy white make up needed.