Aaaaand Dune .
Space Opera, possibly the first, definitely the archetype. Lasers, knife-fights, duels, monsters, romance, sex, MEIND-EXPANDING DRUGS , nobles, stormtroopers, magic: you name it, Dune 's got it. In the first book at least. After that, well... well the first book is good. Really good. You want to know how this whole fantasy-in-space thing started, you read Dune . Full stop.
Upon rereading it for the second or third time (when I first read it I was waaaaaay to young, 9 or 10 or so) I noticed myself liking the later books as well, with their enormous scope. Probably why I like Foundation as well, it's really ambitious and pulls it off (though Dune falters a little bit towards the end).