I started thinking about this, and I really want to say Dragons; once the PCs have made it to Level 5 or above.  However, at lower levels, Dragons can be overkill.  A pack of Wolves can be a Big deal at lower levels; as well as anything that can Fly.

People.

Intelligent adversaries tend to be best; dragons are usually great. I'm liking Stonehell's Vrilya who are sort of like dark elves or Melniboneans with arcanatech.

Quote from: Razor 007;1056774I started thinking about this, and I really want to say Dragons; once the PCs have made it to Level 5 or above.  However, at lower levels, Dragons can be overkill.  A pack of Wolves can be a Big deal at lower levels; as well as anything that can Fly.

And freaking Owlbears!!!  Some of the early classic monsters are timeless.

Quote from: Razor 007;1056793And freaking Owlbears!!!  Some of the early classic monsters are timeless.

I agree with this.  Something about the old guys not only normally have strange and unique abilities but have so much lore and history of the game just baked into them.

If I had to pick one, I would go with Displacer Beast.

It looked frightening and strange and seems to be a creature from some strange alien ecology right at first glace... then you realize that it isnt even where you think it is....that's terrifying.

Hi everyone.  This is my first ever post here.

Man I have to go with Dragons or Humanoids

Quote from: James;1056885I agree with this.  Something about the old guys not only normally have strange and unique abilities but have so much lore and history of the game just baked into them.

If I had to pick one, I would go with Displacer Beast.

It looked frightening and strange and seems to be a creature from some strange alien ecology right at first glace... then you realize that it isnt even where you think it is....that's terrifying.

Hi everyone.  This is my first ever post here.

Welcome.  I think the displacer beast was inspired by the Coeurl in the A.E. Van Vogt story "Voyage of the Space Beagle".  So strange alien ecology is quite a fitting description.

Quote from: Franky;1056893Welcome.  I think the displacer beast was inspired by the Coeurl in the A.E. Van Vogt story "Voyage of the Space Beagle".  So strange alien ecology is quite a fitting description.

See, that right there is exactly what I mean.  I was rather young when I looked at a monster manual for the first time, but the game had been out for many years already.  So I had the advantage of seeing all this stuff after much of the lore had already been established and it felt literally like I was stumbling into this strange new world that had it's own history and stuff behind it.  But, it only gets hinted at in the MM and without the internet back then to really delve into this stuff, you were left to put the pieces together on your own.  It really was a fascinating time to come into the hobby.  

More on topic.
Gelatinous Cubes also come to mind. Because you are now in a world where wizards have giant transparant living creatures made of acid acting as a tireless roomba.  And I think that's pretty cool.

1.  Humanoids for versatility.
2.  The crazy oddball monsters (owlbears, driders, displacer beasts, beholders, etc.) just because they make for interesting encounters.

...and welcome to RPGsite, James.

Gelatinous cube...that reminds me.

I used to have gelatinous cubes come in various colors and flavors.  Mine were edible after death, because I was twelve and thought it was funny.

And weak against fresh pineapple.  Went through a phase where I used the damn things constantly (way fucking overkill, looking back) and the party carried pineapples hanging off their belt as standard equipment. Mage developed an Explode Produce spell.  Got into some heated discussions about procuring fresh pineapple in a snow zone.  Cleric eventually lobbied for Create Food and Water to do the trick, so we redubbed the spell Create Fruit and Water.  Good times!

Hmm, very tough call. I like most of the classic monsters. I can't say I really have a single 'favorite'.

I love imps and mephits, most especially in Planescape. Chaotic Asshole is super fun when the PCs need what the little bastards know (or claim to know).

I assume the implication here is D&D or D&D-eqsue, so my answer is Giant Frogs.
They're a fun challenge and unexpectedly deadly, especially to small characters.

//Panjumanju

Ogres. So much rage, so little wit.

For me, gotts be the undead. The dark reflection of our own mortality. A path to immortality through dark powers.

As a GM, they offer tons of versatility. Power level from starting schlubs of PCs to world-shaking elder vampires and liches. They can be mindless or have intent. Some stay in their graves with their treasures, some come knocking on your door.

And it's almost October, the perfect time for undead!

I'm going to second dragons.  All but the smallest come equipped with a mini dungeon and all of them have a hoard of treasure.  It makes for fun all around.