First person Adventure is not just about exploration, it's also about puzzles, narrative and non-twitch actions. Metroid Prime is an FPS since reflex based actions are dominant.

If you really want to know what an FPA is, then check the Penumbra series. That's a true FPA. 

 the_bloodwalker said:

There's already horror FPA : the Penumbra series. And I heard it's quite good.

Deus Ex is an FPS/RPG. God do people never check their genres correctly?!

It can also be considered a first-person action-adventure game.  I thought that was close enough to what this thread is actually talking about.

I think developers will be inclined to add more and more new features and playable instances to FPS games that differ from common practice.
The level of saturation in this genre is almost like no other, and in order to maintain high sales one has to reinvent the genre pretty soon, I for one am getting rather dizzy trying to distinguish these games from one another.
Deus Ex 1 & 2, Thief (technically a medieval FPS setting), Dark Messiah (I actually enjoyed that), Condemned and S.T.A.L.K.E.R are examples of dev's actually trying to set themselves apart and I commend them for it!
10 years from now, I don't think we'll recognize shooters or FPS', at least not if we try to identify them by the old standards and set bars.

Deus Ex has adventure elements in the game (I beat it, I'm sure you probably have as well so you should know exactly what I'm talking about).  I'm not saying it doesn't have rpg elements in it, it does, but it also has adventure elements in it as well.  It's a hard game to classify because it has elements of several genres in it...

http://en.wikipedia.org/wiki/Deus_Ex

"Deus Ex takes place from a first-person perspective. It was designed to incorporate gameplay elements from four types of games: role-playing, first-person shooter, adventure and "immersive simulation", the latter being defined as a game in which "nothing reminds you that you're just playing a game".^[11] The player assumes the role of JC Denton, a "nanotech"-augmented operative of United Nations Anti-Terrorist Coalition (UNATCO).^[12] This nanotechnology is a central gameplay mechanism, and allows players to perform superhuman feats."

And here are some websites who chose to describe it like I have...

http://www.gamespot.com/pc/rpg/deusex/  (describes it as a sci-fi action adventure game)

http://www.gamerankings.com/htmlpages2/250533.asp?q=deus%20ex (describes it as an action adventure game)

It does have some adventure elements, but the predominant elements are from FPS and RPG genres, so it's called FPS/RPG.

And also, when you think about it, the adventure elements in Deus Ex are also elements that are almost always present in RPG's: exploration, story-centric, dialogs.

How about a first person shooter where you play as a pirate. Not only would you have guns but you would have swords too. The game would have destructible environments and they could throw in light RPG elements for good measure. You could kill innocent bystanders if you wanted too. Any thoughts, opinions...?

a FPS where everybody is naked

I think you're missig the point.

All first person games require reflex based actions. In order to make the players feel like they are actually the one behind the HUD or camera or it will make no sense. they can be in the use of guns or swords.

 MP, even tough it gas action moments, the key is about exploring the world, looking for secrets, knowing what's going on in the world and get what's necesary to complete the main objective of the game. If you look at those elements, MP is an FPA.

 Penumbra is another FPA, but manages to separate more from the FPS than Metroid Prime. I'll check it out :)

Another big element in FPAs which hasn't been discussed in this thread are boss fights!

I loves my boss fights. You don't find real bosses in most FPSes.

I think it's pointless to argue over exactly what genre these games fall into. Game genres simply aren't that cut-and-dried or well-defined. I think classifying Elder Scrolls games and Deus Ex as FPAs is very defensible. I'd like to note that Deus Ex had several boss fights, while Oblivion had one.

Whether they're FPAs or not, I've enjoyed all the games mentioned in this thread which I've played.