Difficulty Model for Competitive Programming

Estimates the rating that required to be able to solve a problem with 50% chance. It is considered to be a de facto difficulty criteria in competitive programming community.
Available at AtCoder Problems.

FFXIV Crafter Solver

Available here.
Solvers for in-game item crafting of Square Enix's FINAL FANTASY XIV MMORPG.
Advisor: ID-DFS based algorithm to find the best action of a given state and stats. Designed for expert recipes.
Macro: Simulated annealing based algorithm to find the best macro that works under any status changes. Designed for non-expert recipes.

Others

See GitHub repositories for more.