In Gothic 2 and many other games, just grab a ranged weapon and find a spot the enemy can't reach you. Then shoot until they die with no fear because they will stubbornly keep trying to attack even though they can't get you. They never run or find cover.

When it comes to bizarre things that can be found in RPGs nothing is going to beat a weapon called "Tödlicher Schwengel des Stoßens" which can be found in the German version of Diablo 2.

And to all Germans who understand what that item name means: No, I'm NOT making this up! :-) This item really exists.

Well there was this one time in Fallout 3. I had my house set up in Megaton, decked out in pimp style with my robotic Mr Handy butler. Also had one of the local girls pimping herself out around town for me to make some money.
One day I come home to find the Mr Handy robot screwing the hooker (Mr Handy indeed). If that's not bizarre enough by itself, the fact that Mr Handy actually paid her afterwards definitely was.

Oblivion:

- Nerastarel's House: The inside of the house is breaking down and ruined, but the outside is perfectly fine. It is filled with undead; but there is no reason given as to why the house is infested with the undead. There isn't an NPC in the game named Nerastarel. No one in Skingrad, or even the entire game mentions the house.

- There is a burnt down village. The residents wear ragged clothes. None of them will talk about why the settlement is in such a state, and everyone goes about their day as if nothing ever happened.

Skyrim; cold water and swimming:

- Arctic waters can kill a man in seconds, but your character can wade through it without repercussions.

Edit: formatting

I remembered a rather interesting thing that can happen in Ultima 6.

In Ultima 6, there is a place where you can buy staves. A staff will come without any magical effect, but by casting the Enchant spell, you can place a charge on the staff, which can then be used by using the staff as an item (much the way you'd use a spellbook, but without picking a spell at the time of cast).

Ultima 6 also has a spell called Animate, which will turn an item into a creature. If the item is holding anything, whatever it's holding will drop to the ground. Now, items you generally think of as containers (like chests and bags) can't be animated, but some other items, like spellbooks and staves, can be. Animating a spellbook will cause its spells to fall onto the ground, allowing you to put only some of the spells back in or move them to a different spellbook.

On the other hand, animating a charged staff will cause its charges to fall onto the ground. Yes, charges are in fact objects that can fall out of a staff. Charges appear as the white letters "CH", can be walked over (like ground or most items), but can't be picked up (like ground but unlike items).

Does this make any sense?

There's other trickery that can happen in Ultima 6, like using Magic Lock spells to overwrite key-required locks with locks you can open with Unlock Magic, using Animate and Clone to duplicate items Replicate doesn't work on, and many other bizarre tricks that can be done.

Found another one in Morrowind:

In the town of Gnisis, I find a shopkeeper who happens to have some moon sugar in stock. I buy some, then try to barter with her, and she says she'd rather not have any trouble and doesn't want to deal with the moon sugar.

Does this make any sense at all?

(Merchant offers illegal goods for sale, but refuses to trade with anyone who already has those illegal goods, even if they just bought them for sail.)

I've always been baffled by glass armor in Elder Scrolls games. Glass doesn't sound like a good material for armor and even more puzzling then it's categorized as light armor and not heavy armor. Maybe I'm missing something there but armor made from dragonbone makes sense - armor made of... glass really doesn't.

It is not really glass as we know it, but a lightweight volcanic crystalline metal-

[url=https://en.uesp.net/wiki/Lore:Malachite]https://en.uesp.net/wiki/Lore:Malachite[/url]

That reminds me of the Glass Sword in Final Fantasy Legend 1 (English version of SaGa 1) and in the SaGa 3 remake. You have here a sword made of glass, that appears to shatter on use (in FFL1, the game tells you it shattered, while in SaGa 3 DS the animation shows the sword shattering), yet the weapon can be used multiple times (50 in FFL1) before it actually breaks.

(In the Japanese version of SaGa 1 and in SaGa 2 (all versions), the sword has only one use, while original SaGa 3 doesn't have this weapon in the first place.)

Then again, SaGa 1 and 2 have a chainsaw that lets you saw apart enemies into bits (depending on the attacker's STR and the defender's DEF), so there's that.