Blade Runner - it is the best adventure game of all times. Story is incredible and it is mixing original story, P. K. Dick book story and movie story. It has multiple endings, it is detective style adventure (not use rubber duck on flying holly rabbit to make it cry and turn into pigdog 2000) and it has amazing gamepaly. It is only game that I have had finish more than 10 times :D And I still want more!!!!!!
Check it out here:
Blade Runner Video Game on IMDB.com
Blade Runner on mobygames.com