Acid, ow. Nasty. Just does damage, that's all.
Laser Charges are a blast to throw at things, just not at Robots!
Sunspot Urchins can and should be thrown! Try a few! A pyromaniacs dream come true... Craft yourself an Ultimate Fishing Rod and go fishing in lava to get a few of these. Extra damage to Creepers! :)
Water Balls are really useful in multiplayer. Throw one at a friend on fire! Also does just a little extra damage to Creepers, but not much.
Dead Irukandji are difficult to obtain, but totally worth the risk! The problem with getting a dead one, is that you have to get close enough to kill a living one first! DO NOT TOUCH a live Irukandji with your bare hands. Instant death will result. Itty bitty teeny tiny little critter. Most deadly venom on the planet. Go figure! Can also be used to make Irukandji Arrows for the Skate Bow for better distance and accuracy.
Acid - ow.
Laser Charge - robots are immune!
Sunspot Urchins - sets everything on fire!
Water Balls - puts out fire on your friend!
Dead Irukandji - 100, yes you read that right, one hundred attack points.