This is my first successful arduino project. It is a simple Simon game where the objective is the repeat the random sequence given to you in the correct order or else you lose. It took about a week to write the code and a week to build the circuit. It was fun to make and I would definitely recommend building if you are an experienced coder looking to create some hands on projects with the arduino.
My code made from scratch is here (http://gv-8.com/arduino/simonhtml.html). I used the TrueRandom class (http://code.google.com/p/tinkerit/wiki/TrueRandom) to randomly choose the sequence, then I display it. The amount of rounds until the game ends and the number of colors per round were constants so they are very easy to change for difficulty. This is probably not the most efficient way to write it but it works.
The circuit consists of 3 button switches that require 5V+ and a specific port on the negative side. Also, there are 3 LEDs which require GND for negative and a specific port for the positive side. For the 3 LEDs we (my dad and I) connected the 3 negative sides together and connected that one common wire to the ground and the same for the 5V+ for the 3 switches.