* Emulator and debugger for a particular embedded hardware (MSP430)
* Website that scraped Rosetta Code and displayed it in a less-annoying form
* Genetic algorithm for graph problems
* Nand2Tetris course
* Two weeks trying and mostly failing to learn Haskell (took me another year to really 'get' it)
* All sorts of other fun/dumb stuff. Boggle solver! Endless project Euler problems! Super Meat Boy!
In Rust, everyone is a print debugger. The only thing that really goes wrong in normal code (once it compiles) is "why is this value not what I expect?". Dropping down into GDB is way overkill.