Commodore VIC 20

Among the cartridge expansions, there was RAM (even a stunning 32K ! Just think what you could do with that) and a combined RAM + graphic_commands_for_BASIC which allowed you to paint circles and lines and rectangles at a resolution which was something like 180x200. On the typical TV we were using as a monitor, that made for really big pixels.

The Commodore Basic language and the crampedness of the RAM gave me bad programming habits which took me years to get rid of.
I also remember a cartridge game called Radar Rat Race, which I played with guilt because I knew that I should be programming instead of running around a maze.

Another memory of those years was reading all of the monitor program source in one afternoon (6502 assembler, of course), and constant squabbles with my father that wanted (rightly) to watch the RAI TV news, while I wanted to keep using the VIC 20.

You might also tell us something else about the machine:
• 6502 @ roughly 1MHz
• RAM expandable to 40kB
• Cartridge port
• 22 column screen
• Cassette and *floppy drive* ports. (yes, you weren't restricted to the lowly Datassette for your storage needs)
• One Atari compatible joystick/paddle port
• User port with TTL level RS-232 serial port

The user port, cassette port and floppy port were all compatible with the C-64/128 among other CBM 8-bitters.