Actually a real-world fungus, just heard about it. A fungus that tastes well and all, no ill effects. UNLESS you consume some beverage, even 3 (three) days after eating it. Then you become really sick, pains, vomiting, all the fancy stuff. Was really used to cure alcoholism. May be a joke or to make sure the heroes spend their time focused on the mission.
Plant that is likely to produce allergic reactions in almost everybody, even by touch. Usage: medicinal, in very exotic foods, non-lethal traps, disabling opponents (have you ever cut an onion,anyway?), spell components, etc.
A local fungus-breed explodes if hit or fallen upon. If there is any conflict between inteligent enemies,both sides are likely to use it to their advantage.
The PCs are exploring the catacombs beneath a Colosseum-in-Rome type of structure, when they come across a foul-smelling, stagnant, ankle-deep with algae, public mass latrine. Countless urinals of marble, line this rather large chamber equally crafted of marble. Whatever system of plumbing once worked here, has not in many years. Old graffiti lines the stained,dirty walls, prominently bolded are such intellectual poetic musings as, "Urine For It Now", "I Pee Therefore It Comes" and "Now Urine Trouble".
A few moments after the PCs get to take in this unpleasant location, they hear the low rumbling of ancient plumbing and rather large Urine Elemental rises like a great, wet, wave of filth to attack them. The creature reeks and exudes noxious debilitating fumes, while its liquid strikes burn flesh like acid.