I think that I would get alot of criticism for even thinking about these job combinations but I've been playing mages for waaaay too long and wanted to try something "new". Here's a list of what I thought would be nice to see and explinations:
Sam/Rng: I think this combo would be like super duper SCer. Not only would you have awsome TP gain but you would get the benefits of ranged weapon skills too! I can't really find a fault for this combo except for the fact that alot of people want Samurai's for 2nd voke and such.
Rdm/Nin: This combination would probably work best if you were a Taru cause you wouldn't have too little mp. Also, you could dual wield swords/clubs and actually get some tp/int/mnd.
Nin/Rng: Welllll...... so not the greatest idea cause you can't tank/voke but I have noticed that a lot of Guns and Bows can also be used by nins. With katanas and strong ranged attacks with the weapon skills of both I think they would be very effective damage dealers, perhaps better then Rngs. Rngs mostly use knives which do so little damage whereas nins can use katanas which do more damage then knives.
Smn/Brd: Those who are not summoners probably think this is the stupidest combo but I know a few smns that detest main healing. I mean, if they wanted to be a healer, wouldn't they have chosen whm? But anyways, a smn/brd would be like the ultimate buffer. At the same time, they could melee because they don't have to worry about standing back and casting spells. They can stay with the melees and constantly use whatever buffs they want.
Hrm... I can't think of anymore right now but feel free to comment on these ideas or add more. I want to find a really "different" job combination that will work ^^.