Cheap, cheerful and fun to drive, you mentioned it. The SVT Focus is a great choice. I loved mine. I miss it. FWD but still fun. Easy to work on and cheap parts. Even making it go fast is pretty cheap.
As for RWD cars, well, that's a short stack for under $12k. I ruled Bimmers out myself when I was looking due to their expensive maintenance and repairs. It's just plain ridiculous!
Honestly, if you're just looking for cheap temporary fun to drive transpo for the time being you should consider fully repaired, rebuilt/salvage titled vehicles. You can't beat them for the price and Ebay is loaded with them most of the time.
Here are a few cars that I'd consider. They can be had for $12k easily:
2000-2001 Audi S4 (salvaged)
2002-2004 WRX's (salvaged)
2000-2002 Lincoln LS
1995-1998 Lexus SC's 300/400
1993-1996 Nissan 300ZX
I'd hit THIS!1996 Impala SS
Another hitable rideOld School
1989 Conquest TSi, old, but cheap and fun IF you can find one.
1988-1992 Toyota Supra, turbo of course
1991-1992 Toyota Celica All-Trac, rare as hell, but FUN!
Hit it for the hell of it 1991-1992 Galant VR-4
