Speaking of Bahamut, if you're familiar with Final Fantasy and are playing the La Mulana remake, it feels strange when you kill this water fish boss and the game declares that "You have defeated Bahamut", especially since Bahamut is one of the earlier bosses in the game.

Also, in Elminage Gothic, there is a regular enemy called Bahamut. Yes, Bahamut is used for a normal enemy that can appear in random encounters and, aside from its name, isn't particularly notable.

Does Daedra appear in first TES game? No. Still it is iconic TES monster.

Goblin is just generic D&D monster (nothing bad about Goblin being generic). Also game doesn't have to have flagship monsters. Lunar comes to mind - most monsters are classic fantasy. Might and Magic series is another example of games without any apparent flagship monsters.
Yeah, they aren't purely monsterish. Still, iconic creature nevertheless. They appears as monster, as neutral/friendly creature and even as summon.

Fallout 1-3:
Rad-scorpion
Super mutant

Mario:
Goomba

Star Wars:
Stormtrooper

Gothic:
Scavenger

LIMBO:
Giant spider

Prince of Persia 1:
Palace guard

Bahamut basically means "Ancient Beast". Variation of "Behemoth". Doesn't have to be a dragon-like creature. Final Fantasy is especially interesting in this aspect because it has both - bahamuts and behemoths.

Fallout (all games)- Deathclaws.

Japanese are remarkable for drawing inspiration for their games and media from pretty much any "obscure" (by Japanese standards) mythologies and creatures. Bahamut is not something created for Final Fantasy games, they got the name from a mythological Arabian creature. They also use a lot of names of characters and places straight out of Norse mythology and even French/Breton lore (the Ys games, for instance, are based on an actual Lost Islands myth that speaks of a mythical city -- much like Atlantis -- named Ys that disappeared into the sea). Efreets/Ifreets, Kobolds, Sirens, Gryphons, Harpies, etc. all come from old Arabian, Norse, Greek, Roman, Persian, Norse mythologies and medieval bestiaries. Heck, even names like Behemoth and Leviathan are taken straight out of the Bible!

They've completely lost their terror-inflicting aura in Fallout 3. :(

They can still kick your ass though, as long as you don't build the dart gun, which is totally fucking OP.

For me the Ash Vampires are the most memorable MW enemy.

There is no game that is just called "The Elder Scrolls"; the first game had the subtitle "Arena". There is, however, an old game (for the Famicom/NES) called "Final Fantasy" (notice the lack of a number) that lacks Marlboros, etc. (Yes, I am being a bit pedantic here.)

There is a game called "Dragon Quest" (again, no number) and it actually does have Metal Slimes (which, IIRC, yield 105 experience, the most of any enemy in that game).

Disgaea Series :
Prinny

Shin Megami Tensei Series :
Jack Frost

Kingdom Hearts Series :
Shadow

Minecraft :
Creeper

Pokemon :
Pikachu

The Dogoo from the Hyperdimension Neptunia series

I disagree. For me, for a game to be an RPG, combat (and preferably other things as well) needs to be decided based on the character's skill, not the player's.

To put it another way, in an RPG, the player tells the character what to do rather than directly controlling the character herself. That distinguishes RPGs from, say, action games.

Also, don't forget that non-RPGs have leveling systems in some way (for example, powering up your whip in the original Castlevania).

One more question: How would you classify a game that is similar to a typical Dragon Quest game, except that there is no leveling system (but combat is still turn based)?

Personally I've always thought that RPGs were best characterized by a system of stat/level growth. A player's characters would almost always begin a game in a fairly weak state and would be unable to handle all but the most basic and common enemies. However, over the course of the game -- and especially as a result of the player's actions and direct commands in battle -- the player's character would be gradually transformed to be able to fight progressively more difficult enemies. Therefore "control" in the sense of telling a character what to do still relies on a certain degree of player skill that is comparable to any other game.

The difference in my interpretation of an RPG from say, leveling up a weapon in Castlevania or Super Metroid, is that these other games focus on improving equipment but not necessarily the player's character. Therefore, growth becomes less individualized in the context of these other games as the player cannot change fundamental aspects of their character, limiting the degree to which a player may actively engage in "role playing" . Of course there are many exceptions to this rule, and genre boundaries are routinely blurred making the whole business of defining the critical elements of an RPG somewhat difficult... To side step this whole issue, I simply think of RPGs (or RPG-esque games) as having some form of stat/level growth. :p

Finally in regards to your last question... I can't think of any game in which a player might engage in a system of turn-based combat without actually experiencing the rewards of stat/level growth. Heck, even strategy RPGs rely on some form of character growth to improve a player's units over the course of the game.