fantasy animal?
Gryphon

giant version of (Or shrink me down to the right size for)

butterfly
dragonfly
bat (I'm male)
flying dinosaurs

the really, really fast birds

something that looks like a baby seal but is of legal age ...

But Senator Fetal Snacks had me laughing all through my walk home...

Er... Nope, I have no fuzzy fetishes... and I used to read Omaha the Cat Dancer!

In non fantasy-animal-sex news,

Pope Shenouda made my week. Thanks.

I would love to go with a big cat too, but as a woman, I have to say ouch, and no to that. You know, barbs and all... So I'll go with a wolf.

As for fantasy creature I might go with an Elf. Or maybe an Angel.

Not sure about the real animals, maybe some kind of large bird for all the tickly warm feathers?

In regards to the fantastical ones I think I'd have to go with a dragon, size, uh, permitting. All sorts of interesting leathery scales and bumps and ridges would be involved.

Well, lets see what does failblog have to say about this... [mildly NSFW] http://failblog.org/2012/04/03/epic-fail-fail-nation-lookin-for-a-porkin-fail

If we're talking totally cognizant sentient animals with the ability to be consensual (and sensual?) on our wavelength, then I guess if I were attracted to one in that way, then after all those disclaimers, and adding on that I could breathe underwater, then I would ask a manta ray.

Manta ray fantasy lay. Hmm.

The devil, but only if I can wear a nun outfit...

So, in other words, which Thundercat would I get busy with?

Threesome with Moose and Squirrel!

Moose because... well... size matters.
Squirrel adds the tickling fun.

I think John F's answer is closest to my reaction to the question. Yeah Elves.

It seems likely that this actually happened enough times in our past for non-african modern humans to carry some Neanderthal DNA. Surely some people did, and perhaps do, have attractions to more distant cousins (like gorillas and chimps) but these romantic evenings did not result in offspring, so the genes that make these kinds of attractions are less common.

There are plenty of examples of plants that trick other species into having sex with them. Wouldn't it be weird if there were plants that presented flowers which imitated what humans typically find attractive.

I'd have to say that a doe would be an interesting experience...

By the way, the whole concept of tentacle porn is the complete lack of control; it doesn't have to involve real tentacles if you can get someone to concede all control over their sexuality and, well, their actions as a whole, to someone or something else.

I was thrown off the bus this morning, for shouting at my ipod like a crazy man.
GEO: .. fantasy animal.
ME: Cougar.
GEO: .. mountain lion ...
ME: It's a joke about cougars, right?
GEO: .. big comforting paws ....
ME: Cougars. Just say it, then we can move on.
GEO: ..jaguars...Aslan..some big cat...
ME: COUGARS, FFS. COUGAR. JUST SAY THE FRICKEN WORD, COUGARS.
GEO:Filming films is an expensive business...
ME: HE DIDN"T SAY IT! HOW CAN HE NOT SAY IT? WHAT IS WRONG WITH YOU. COUGARS!! COUGARS!! COOOOFRICKENGAAAARS!!!
ME:But this is not my stop, officer.

Satyr, definitely satyr

You say the things few have the chutzpah to say, for better or worse.

I have to say, as a woman, the logistics of your question are quite different, and limiting. I mean, OW.

But tentacles could be fun.

Unicorn?

Maybe I'm not understanding the question correctly (or maybe I'm just boring), but I can't imagine wanting a sexual/sensual/romantic experience with any non-human entity unless it resembles a human so closely that the distinctions border on trivial.

That pretty much limits me to mythological creatures, and even there, I'd have my boundaries. Elves? Sure. Dwarves? Probably not. Orcs? Definitely not. Angels? Sure. Demons? Sexy devil girls = hell yes, scary thorny red rage-monsters = no.

Christina Applegate (humans are animals also)

Geo, you took me way out of my comfort zone with this one.