Anybody who's played GoldenEye will have noticed that on the Statue level it's possible to get >100% accuracy. This is because the automatic shotgun weapon you get hold of fires five bullets per shot. If you hit with all five, that's five hits per one shot = 500% accuracy. Obviously misses earlier in the level will decrease this.
But you can do better. The Cougar Magnum bullet will go straight through guards. Line up six or more and you can get 600% plus. How? Turn on Invisibility and All Weapons so you have access to the Magnum, then go to the Train level. Ignore all the guards until the first long corridor, then try to get as many lined up as possible. Then, blam! Six (or more) down at once. Quit the mission. 600%. Done.
But you can do better still. Turn off Invisibility and turn on Invincibility and go to Control (you can't be invisible otherwise Natalya doesn't operate computers for you). Slap every guard you find to death and proceed through the level until you reach the very first mainframe. Look left to see a door which is usually locked. Carry on through the level until Natalya begins her lengthy hacking bit. Now the door will be unlocked. Ditch Natalya and go through the door to find an area with lots of lockers in a row, and some body armour, and some guards. Take out the guards (all with fists, remember!) then line up behind all ten lockers and fire a single Magnum shot. For some reason, shooting the locker counts as a hit. Exit now and you've got 1000% accuracy.