There used to be a game called Warzone - it had a samurai force called Mishima - they still appear on e-bay from time to time - though, i imagine it would be hard to find enough to make an army out of, so Wper's suggestions are probably better. On the plus side, they and the Urban Mamoth guys have guns. The Warzone figs are a fair bit bigger than IG, though...
Anyway,, in case you are curious what they look like, here are some I painted:
BTW, there are other weapons than the machinegun (I think there is a grenade launcher as well), but they are harder to find. There are other styles of Mishima figures too - some look more like Samurai (more ornate armour), some more like peasants, etc.
Inquisitor Psychologis Ruminahui