Here's an old one. Heavily paraphrased, I was on a Cortex Roleplay map and hosting an RPG that was to the effect of taking out a necromancer. We used a hack and slash "relative" rolling system, 1-100 for each combatant, and the higher roll wins. The difference between the numbers indicated how much of a win. There'd be modifiers based on the skill of the enemy. The first six skeletons against the four party members, party unrestricted with a minimum value of 10, and the skeletons capped at a roll of 70.

The skeletons won basically every single roll, so the best the heros were able to do was maybe smack one before getting the shit beaten out of them by a 15-65 roll or something like that. Heros lost literally every time. Of course, it was an unbalanced system that relied too heavily on randomness (that was part of the ridiculous fun of it) but the players lost so much that I had to create an NPC to come in and help, because there was only so many ways the skeletons could whack the heros without killing them outright. NPC barely broke even against one of them. Heros still lost. Deus ex machina = able to just run past the skeletons into the dungeon. Heros were promptly obliterated by the next level of skeleton that won every single roll, and that was 1 vs 4.

And then, under the same system, a time where I killed a dragon with a goblin using a cheap little spear, with dragon rolls between 30 and 110, and goblin roll capped at 45. Goblin still won. RIP dragon >.>

Ridiculous "system" that made for some interesting scenarios...