When I recently purchased the Dungeon Fantasy collection of monsters, I noticed that most of the listed monsters are not "every-game" monsters. It seems to be lacking simple goblins, harpies, etc. Though it's always possible to make these up, I wish there were officially published versions.
Are there other (official) published templates / monsters for GURPS?
Currently the closest thing is the GURPS Natural Encyclopedia. It includes original stats, coverted GURPS 3.0 stats, converted d20 stats, and reference to monsters already published.
Also GURPS Dungeon Fantasy Monsters I has a complete index to all the monster published for the line. It is scattered throughout all dozen books so it is very helpful in see what there.
Finally many of the sentient monsters, orcs, goblins, etc are represented by template from which you build a character.
In my opinion the GURPS line managers have a blind spot to this issue, and the most vocal fans are so used to using the customization features of GURPS they forget how intimidating it looks to newcomers to roleplaying and/or the GURPS game. The situation has been slowly improving over the years.
GURPS Banestorm contains some classic fantasy monsters and races.
There is also the 3rd Edition Fantasy Bestiary, which also contains a lot of classic fantasy monsters. There even exists a conversion of those stats for the 4th Edition.
(Sorry for not giving you the one monster per answer, as I don't have those books here for exact reference.)
I have used a couple of the 4th edition books (series linked above) as well as the older 3rd edition book.
In fact, I ran a really great "Monster Of The Week" modern horror campaign in which weekly prep consisted of flipping through the 3e book and finding something that looked like fun.
Each monster is more than a collection of stats, though. You'll get an adventure seed, some information on the motives, lifecycle, or other background on the creature, and sometimes variants, or ways to re-skin monsters for various campaign types.
I don't have the books in front of me right now, but I can tell you that the books present creative and interesting new monsters and beasts. For example, I remember an alien creature that mimics a house and feeds off of the misery of residents (this was way before Monster House, btw) which I used to great effect as a haunted house in a Buffy or Changeling game (I can't remember right now).
In other words, you're not going to get a thousand different kinds of orcs, you're going to get well thought-out creatures that you'll have fun pitting against your players.
I don't play much in the way of dungeon-oriented games, but these books are my go-to resources for monsters in pretty much ANY game.
Dungeon Fantasy 3: The Next Level includes most of the common humanoids (orcs, goblins, ogres, etc.) as racial templates. While not listed in the convenient bestiary write up used for monsters, it shouldn't be to much work to make a write up.
One other oft-overlooked source for monsters of many types is GURPS: Horror. Each type of fear has one or more monsters statted up for it, which makes this wonderfully written book by Ken Hite (though that's nearly redundant) a Bestiary by itself.
A few more sources: Dungeon Fantasy Adventure 1: Mirror of the Fire Demon has some more monsters, and there are two further instalments in the monsters series: Dungeon Fantasy Monsters 2: Icky Goo and Dungeon Fantasy Monsters 3: Born of Myth & Magic.
