Really guys? Nobody remembers anything noteworthy?

Fine, I'll go second as well: http://www.youtube.com/watch?v=I5kNE-EKgCg

I've played Tyrian a lot as a kid and sometimes I still find myself humming the tune for Torm without even realizing.

To me it still has one of the best midi soundtracks of an arcade game.

I'm just waiting for some fool to come in here and reference HuniePop.

I don't think its "artworks" would be completely unexpected, though XD

'

Yeah, it was expected and pleasant :)

I obviously did not mean that type of artwork (though it would be interesting to see if anyone will mention any unexpected erotic art they found in games).

It can be anything that you did not necessarily expect to see in a game, and would, in its own, have artistic value. Or it could be something you did expect to see in a game, but exceeded your expectations.

Let me see... like the level and weapon design in Drakan: Order of the Flame. And let's not forget about Rynn.

I have very fond memories of that game - we really need it here on GOG!

Well, it's a bit generic, because any game that impressed me had something that exceeded my expectations.

Anyway, one bonus thing I remembered on the fly:
Tyrian hidden midi jukebox with its 3D "waves" (low quality video here)
(plus its great midi music)