This is an edited version of the original list. I have removed challenges that have no interest to me (mostly booru/chan board stuff) as well as challenges that require me to install additional software, require a different OS, or involve real life components (computer boards, VR headset, etc.).

Practical
Algorithmic
Artificial Intelligence
Compiler/Interpreter/Debugger
Emulation/Modeling Games

🟢 - Easy
🟡 - Medium
🔴 - Hard
⚫ - Ridiculously Hard

1. 🟡 Download Manager
2. 🟡 Make an elastic producer/consumer task queue
3. 🟡 IRC Client
4. 🟢 Markov Chain Sentence Generator (Include Shitposting Capabilities)
5. 🟡 English Sentence Parser that Points to the Context of a Sentence
6. 🟡 MIDI Player + Editor
7. 🟡 Stock Market Simulator Using Yahoo Spreadsheet Data
8. 🔴 Parametric/Graphic Equalizer for .wav files (make it real-time)
9. 🟡 Graphing Calculator (BONUS: Graph the Function's Derivatives)
10. 🟢 To-Do List Application (Web app or CLI)
11. 🔴 Verlet Integration (Verlet Cloth)
12. 🟡 TCP/UDP Chat Server + Client
13. 🔴 Music Streaming
14. 🟡 Shazam Clone
15. 🟢 Chatbot (with conversation retention)
16. 🟡 Paint Clone
17. 🟢 Image to ASCII Art
18. 🟡 Image Converter
19. 🟡 ID3 Reader
20. 🔴 Sound Synthesis (Sine, square, sawtooth, etc...)
    • ⚫ Add Realtime MIDI Playback with Custom Instruments)*
21. 🟡 Password Manager
22. 🟡 Key Press Bot
23. 🟡 IP/URL Obscurification (http://www.pc-help.org/obscure.htm)
24. 🟡 Radix Base Converter (Given a radix base, convert it to decimal)
25. 🟡 Encrypt a file, and upload it online
26. 🔴 Make a Text Editor that autosaves and includes the date in the filename
27. 🟢 Create an HSV Color Representation
28. 🟡 Window Manager
29. ⚫Basic Relational Database Software (SQL Support, Handle Relationships, Focus on Efficiency)
30. 🟡 Pixel Editor
31. 🟡 Markdown (HTML/XML) Editor
32. 🟡 IP Tracking Visualization
33. 🟢 Port Scanner
34. 🟢 Old School Demo Effect (Plasma, Tunnel, Scrollers, Zoomers, etc...)
35. 🟡 Bellman-Ford Simulation with at least five vertices
36. 🟡 Matrix Arithmetic
37. 🟡 File Compression Utility (Make it a GUI)
38. 🟢 PDF Tagger
39. 🔴 Nonogram Generator and Solver
40. 🟡 Calculate Dot & Cross Product of Two Vectors
41. 🟡 Bismuth Fractal
42. 🟡 Seam Carving
43. 🟡 Bayesian Filter
44. 🔴 WMS viewer that isn't web based

45. 🟢 Fizzbuzz (BONUS: In assembly)
46. 🟢 RPN Calculator
47. 🟢 Counts occurences of characters in a given string (include support for unicode characters)
48. 🟢 Towers of Hanoi
49. 🟡 Music Visualizer
50. 🟡 Unicode Converter (Support for UTF-8, 16LE, 32LE, 32BE)
51. 🟢 Calculate the first (n) digits of pi
52. 🟡 Least Squares Fitting Algorithm
53. 🟢 Given an array of a stocks values over time, find the period of time where the stocks could have made the most money
54. 🟢 Highest Prime Factor Calculator
55. 🟡 Hide and Extract Data in images (Basic Steganography) (Bonus: include .gif support)
56. 🟡 Web Page Crawler
57. 🟢 Password Generator (Let User Choose Options)
58. 🟡 Vignere cipher encryption/decryption
59. 🟡 Game of Life
60. 🟢 Caesar Cipher Cracker
61. 🟡 Dijkstra's Algorithm
62. 🟢 ROT 13
63. 🟡 Program that displays MBR Contents
64. 🟡 Random Name Picker
65. 🟢 Encrypt/Decrypt Text : Implement at least one from http://rumkin.com/tools/cipher/collection
66. 🟢 Youtube to MP3
67. 🟡 Text to Hexadecimal/Binary
68. 🟡 Calculate the first 1,000 digits of pi iteratively
69. 🟡 Sierpinski Triangle
70. 🟡 Mandlebrot Set
71. 🟢 Ulam Spiral

72. 🟡 Sudoku/n-Puzzle Solver using A* algorithm
73. 🟡 Connect-4 AI Player using Alpha-Beta Pruning
74. 🟢 Basic Neural Network - Simulate individual neurons and their connections
75. 🟡 Real Neural Network - Implement a basic feed-forward neural network using matrices for entire layers along with matrix operations for computations
76. 🔴 Convolutional Neural Network - implement a CNN for handwritten digit recognition, test on MNIST dataset (Use TensorFlow, Theano, etc...)

77. 🟡 Virtual Machine with a Script that Writes "Hello, World"
78. Basic Bootloader
79. 🟡 Terminal Shell (Executable Binaries, Pipe System, Redirectoin, and History) (BONUS: make it a GUI)
80. 🟡 HTML + JavaScript Debugger
81. 🟡 Write an Interpreted LISP-like programming language
82. 🔴 Make an application that is capable of mounting filesystems from other OSes using the FUSE model
83. 🔴 Pong Game as UEFI file in color (Hint: http://rodsbooks.com/efi-programming/index.html)
84. 🔴 Design an Esoteric Language
85. 🔴 C Compiler
86. 🔴 Turing Machine Simulator
87. 🔴 Read, Evaulate, Print Loop using a compiled language
88. 🔴 LISP Interpreter

89. 🟡 Chip - 8 Emulator
    • 🔴 Cached Interpreter
    • ⚫ Dynamic Recompiler, use dynarec/jit library
90. 🟡 Double Pendulum Simulation
91. 🟡 Constructive solid Geometry
92. 🔴 Ray Tracer
93. 🔴 Real-Time FFT Spectrum Visualizer
94. 🟢 Generate a Compilmentary Color from any input color
95. 🟡 Generate a 5-Color Scheme from the most dominant tones in any image
96. ⚫General Lambert's-Problem Solve (At least it's not rocket science... oh wait)
97. 🔴 TI-86 Emulator (Bonus: Include the Option to Create Programs)
98. 🟡 N-Body Simulator, with particles having a certain mass and radius depending on the mass that merge if they collide (Bonus: Include a GUI where you can place particles)
99. 🟢 Eulerian Path
100. 🟢 Draw a spinning 3D Cube
101. 🟢 Cellular Textures
102. 🟢 ASCII Digital Clock

103. 🟡 Knight's Tour
104. 🔴 Monster Raising/Breeding Simulator (Like DragonVale, My Singing Monsters, etc.)
105. 🟡 Tetris
106. 🟢 Snake
107. 🟡 Pipe Dreams
108. 🟡 Pac Man, with different behaviors for each ghost
109. 🟢 Rock Paper Scissors
110. 🔴 First-Person Engine in OpenGL (Walking, Looking Around, Jumping on Obstacles)
111. 🟡 Shuffle a deck of cards (Include visualization)
112. 🟡 Simulate a game of tag using a multi-agent system
113. 🟡 Scorched Earth clone
114. 🟡 Minesweeper
115. 🟡 Audio/Visual 64KB Demonstration
116. 🟡 Sudoku
117. 🔴 Danmaku (Bulle Hell) Engine
118. 🔴 Roguelike Engine/Dungeon Generator
119. 🟢 Yahtzee
120. 🟢 Oil Panic
121. 🟡 Chess (BONUS: Add Primitive AI)
122. 🔴 Go (No AI Necessary)
123. 🟢 Connect Four
124. 🟡 Mastermind
125. 🟡 Missile Command Game
126. 🟡 Breakout
127. 🟢 Simon
128. 🟡 Tron