I would probably say either an E30/E36 BMW 3-Series, an Audi 80 or the like, or an old Mercedes E-Class. Wouldn't do an E-Class if you could avoid it though as the prices on parts would probably exceed the price of the car. I haven't seen many of those with manuals though. If you're willing to sacrifice a bit of space on the Merc and go down a bit to a C-Class you can probably manage getting a newer one with more kit. Also been seeing some fairly recent Hyundai Sonatas on carpoint.com.au, those are probably quite good to drive as well.
EDIT: You can also get an original Mini for that money. That's about as unique and fun-to-drive as you could get for 5,000AU$.