Once upon a time (25 years ago now) one of my old friends was DMing a B/X D&D campaign with a small handful of house-rules. They had a huge effect on play.
We rolled out ability scores 3d6 at a time to generate 6 score but we could put the scores where we liked.
Characters had a % chance equal to their dexterity score of being ambidextrous and as such being allowed 2 attacks a round.
I managed to roll an 18 and a 16 or 17 for my high scores. I put the 18 into STR and the other high score into DEX , got lucky and was ambidextrous. So I made the character a Magic-User. A Magic-user? Yes, a magic user. Since 1st level MU's actually fight as well as anyone else in B/X D&D he was actually a pretty fierce combat machine with 2 blows a round doing 4-7 pts of damage each. We had a fighter in the party who was also luckily ambidextrous but he wasn't as strong as the MU. I played my MU like a kungfu spellcaster and the DM was thrilled (I was pulling his DM heartstrings as he was a martial arts nut at the time).
Into play we discovered more little treats to the campaign. Undead returned as the next lower type of undead a few rounds after they were dispatched. Imagine the horror when you've dispatched a couple of ghouls at 1st level when all of a sudden they stand back up... luckily they were just zombies, we beat them as well and then the skeletons stood up out of their mauled flesh... I can still remember the panic and the rout that ensued !!!! All the undead in the campaign were like this, they were unholy horrors.
Poison sickened a character into a virtually helpless state for a few rounds even on a successful save so getting bit or stung by poisonous creatures was a big deal. This was back in the save or die days too so poison was a huge problem. Luckily we discovered the DM had antidotes for poison as a common treasure item for each type of poison, they could save your life if quickly applied or even provide a few rounds of immunity... luckily that is until we realized poison was far more common then in most games we'd played until that point.
Exploding monsters seemed to be a feature of that game also, a kung-fu film inspired horror if I recall correctly. We could usually tell it was coming.
So put your scores where you want, lot's of attacks, undead that just keep on coming, lot's of poison and exploding monsters. It was a heck of a lot of fun.