Hardness protects against all forms of damage.
To gain hardness, use polymorph any object (Player's Handbook 263) to turn a resilient object into a creature, use true mindswitch (Expanded Psionics Handbook 120) with that creature, and wait for polymorph any object to expire. You are now the desired object. This works best for a psion.
Adamantine: hardness 20 (Dungeon Master's Guide 283)
+5 enhancement bonus: hardness +10 (Dungeon Master's Guide 217 and 222 [see errata])
Greater crystal of adamant weaponry: hardness +10 (Magic Item Compendium 64)
Hardening at CL 20: hardness +10 (Spell Compendium 109)
Matter manipulation: hardness +5 (Expanded Psionics Handbook 115)
Soulforged: hardness +1 (Dungeon Master's Guide II 279)
i wonder if some dm's would rule that the lapsing of the polymorph effect would be the same as suddenly not having a body, ergo, you die instantly. otherwise, quite useful. thank you for reminding me about hardness. =D
The Haunt Shift spell can also put you into an object. It's a complex spell (rules wise) so read it over a bunch until you've got it. Also, Obdurium (from Stronghold Builder's Guide) is Hardness 30, while Blue Ice is IIRC Hardness 8 but doesn't have to worry about stuff like Rust Monsters. Dwarvencraft Quality items (Races of Stone) have extra HP and +2 Hardness, and the Augment Item spell (Stronghold BG, again) doubles hardness for caster level days.
JaronK
yes, i recalled obdurium too, as i have that book. excellent catch. i'm not familiar with haunt shift.. which source was that from, please?
Blue ice has hardness 10. It ties with bronzewood (Eberron Campaign Setting 126), deep crystal (Expanded Psionics Handbook 128), dragonhide (Dungeon Master's Guide 283), duskwood (Magic of Faerun 178), and frystalline (Book of Exalted Deeds 38). Sentira (Secrets of Sarlona 135) has hardness 15 and is generally great, since it has the properties of mithral except for being crystal.
i missed sentira, nice addition. thanks!
the statue spell gives hardness 8 basicly all day long
i did not know about this spell, thank you! i can think of some fun stunts to pull off with npcs in the next castle the pcs visit thanks to this suggestion. =D
There are quite a few other highly obscure damage types, but they rarely have specialized solutions. For example, Maw of Chaos deals chaos damage, and the breath of a topaz dragon uniquely deals either desiccation damage or dehydration damage--whichever *isn't* the type dealt by most other desiccating effects! There are even more that I cannot remember offhand, but the only "weird" damage type I can think of with a resistance is dehydration/desiccation, because there is a spell that can shield some of that type of damage. For anything else, I think you're stuck with hardness.
ah yes, i did not specifically mention the desiccation or dehydration damage, good catch.
Zodar (Fiend Folio p.199) is impervious to all attacks except those from bludgeoning weapons. Not a perfect protection but helps at least.
i will have to find a way to look that up, i don't have that book. what kind of creature is that?
Defiant 3 (Planar Handbook) grants immunity to divine damage.
now that's useful too. i can see an npc discomfiting a pc cleric by obtaining immunity to fire and laughing off a flame strike completely unscathed. now if there was only something that did the same for arcane or psionic.
thanks for all the very useful suggestions all, including the ones i did not specifically reply too. it is all very much appreciated!