ok...I played around a bit and for the material weakness shenanagins we have two caste-level tokens...a general and a specific
[GENERAL_MATERIAL_FORCE_MULTIPLIER:1:1000] for example would change every 1000pts of force directed against a creature with this token to 1...so that 20000 rail gun projectile would be reduced to 20. nice.
[MATERIAL_FORCE_MULTIPLIER:INORGANIC:SILVER:1000:1] works the same way, but with a specific material. In this example 1pt of force from anything made of silver becomes 1000. Big problem with this is that creature specific materials do not work, so to make say super mutants take more damage from a securitron's plasma bolt...would have to create a plasma material instead of just using the template.
Another caveat to using this instead of custom materials to boost toughness is that weapons and armor made of creature materials lose their special properties (xenomorph chitin armor wouldn't be any better than cazador)
Oh, there is also a syndrome
[CE_MATERIAL_FORCE_MULTIPLIER:MAT_MULT:NONE:NONE:1:2] Vampires have it as part of their creation...but it could possibly be attached to a timed interaction to make things like personal force fields, or an "entrench" ability
but yeah...I slapped those on two opposing batches of claptraps, gave one group silver machetes & drills, the other group got iron...total slaughter of the iron users.