Commodore 64

The C64 has many different faces - but all incarnations remain compatibility. The best-looking C64 was perhaps the "Golden-C64": As there were over one million C64 in Germany Commodore produced a special series of (officially) 150 C64 in a golden case. Each unit came up with a certificate and a special serial number.
The C64C (Compact) was also full compatible to the old C64. It had a flat case which gave hardware extensions less space.
The combination of C64C and the first C64 had less chips and a new CPU: 8510 which was full compatible to the 6510. This version of the C64 was usually sold as a games system together with a game cartridge and Commodore's joystick.

The perhaps worst basic of all homecomputers - Basic v2.0 - was never changed. The basic forced many C64-owners to learn assembly language and program basic extensions. Therefore most people know their C64 very well. And for the absolute beginner who don't want to learn assembly language, there were hundreds of basic-extensions like Simon's Basic and Exbasic Level II. Some of them are specialized for graphic or interrupts. Other programming languages did not have great success. Comal was used by some people.
Today the C64 is still be sold in some countries. Extension cards like the 8MHz-speeder and harddisks keep the C64 alive.

*arnold.c64.org