Programs suitable for beginners and advanced programmers

Question

What kinds of programs should not only a beginner learn to do? Doesn't matter what programmer language.
Something like from "noughts and crosses" to "tetris"?
Btw: a big recognition to Alexey Leonidovich Pajitnov who developed tetris.
Thank you for your opinion and recommendation!

Answer 1

Sudoku is always fun. You can start with a command-line program and later extend it with a GUI. Text-based RPG in Command-line. If you are less interested in games then you could do any kind of Analyzer. There is a lot of free accessible data in the web that you could process (weather data, crime statistics....)