Apparently the necrotising effect of Loxoceles Reclusa (brown recluse, violin spider) bites bites aren't actually that common, although there are a few more, somewhat nastier species in the related Sicarius species, one desert species, S.Hahnii has been tossed around as one of the most deadly spiders, causing tissue necrosis and widespread systemic toxicity, and as of yet, no antivenom available, probably just as well it spends most of its time in the african deserts
Bakegaku, its not the cowries you want to worry about, but the cone shells, they hunt fish, using a tethered, modified tooth as a harpoon, and carry some pretty potent neurotoxins, the conotoxins, some, I think it might have been one of the alpha-conotoxins have been adapted into extremely potent painkillers that are active when injected into the spine, although nicotinic antagonists, they are on almost a vague similarity to epibatidine in that respect, although the latter is a frog toxin with nicotinic agonist effects.
The wandering spider species do apparently dry-bite in a fair amount of cases, but are really bad tempered sons of bitches, that like the fierce snake (inland taipan, oxyuranus scutellatus) quite often strike repeatedly once you piss them off, and in the case of the spider, that seems to include just about anything, up to and including being in the wrong place at the wrong time shopping for bananas
Some of those tropical nettles are dirty great big stinging trees, some fairly lethal Laportea and Urera species for instance, a few of them have reportedly been fatal, and quite a lot apparently hurt for several months after the sting, I had a bit of a nasty encounter with something of the ilk while on holiday in kusadasi, Turkey, decided to go out somewhere less inhabited, and brushed against a rather unusual looking nettle of some sort, with very compact, spherical green flower clusters, looked quite like say, and unripe and very undeveloped blackberry fruit in structure, covered with what I found out where some pretty potent stinging hairs, I made damn sure to watch out for the same plant in future, after several hours of throbbing pain in my hand and wrist, I also saw colonies of a species of rather mean looking ants, about 0.5-0.75 inch long, dark colored, and with the general appearance of the bull and/Ponerinidae family, the primitive ants such as Megaponera, and the bullet ant, supposed to have one of the most disabling insect stings going around, needless to say I didn't take the chance of getting close enough to get stung, as I didn't much care for the idea of having one or more limbs swell up like balloons or having an allergic reaction and becoming one giant talking hive-wheal
The platypus, at least, the male which has the toxic spur on the hind feet is quite definately venomous to humans, reputedly it digs its spurs in hard, and from my reading on the creatures, extremely painfully, and can cause paralysis, while not usually being lethal to humans, better than sitting on a stonefish, heh, but not something I find a particularly appealing way to spend a week or so
I looked up the wandering spider case again, and apparently it was a chef handling imported bananas who got bitten.