The second you let fly the arrow, you feel the burning in your fingers. The world around you fades as you look down in horror at the crimson thorns that dance on the surface of your hand. You hardly notice that the arrow met its mark - the goblin falls to the ground, pierced deep through its eye - as you, too, fall to your knees. You bellow in pain, the howling echoing through the cavern as the magical vine constricts, the thorns piercing into your flesh.
You fail the saving throw. The curse takes hold of you, the Bane of Thorny Improbability, which damns its bearer to be eternally plagued by probability and combinatorics conundra in their adventures.
You know that you possess an antidote to stave off the worst effects of the curse, but you have three unlabeled flasks at your belt, all of which have an equal probability of being the cure. You choose a flask at random, but as you seek to dislodge it, one of the other flasks falls to the earth and shatters. The liquid eats through the rock of the cavern, giving off acrid smoke, and you recognize that the fallen vial was a deadly poison, not the cure.
Knowing that the second flask did not contain the cure, do you have a better chance of salvation by drinking the flask you originally chose, or switching to the remaining unfallen flask?
I used to DM quite a bit, though I've been a player in my last two campaigns! But I also like watching things like D20 and I read a fair bit of fantasy as well.