For people like me who enjoy building and painting Gunpla I would like to inform you that I have written a book entitled Decals: How to hand paint details on plastic models, Gunpla, and other scale models. Its eight dollars American and is avalible now on the kindle store and free for Kindle Unlimited.
Now that my shameless self promotion is over its time for me to answer the question. My favorite build was my OZ-00MS Tallgeese as the suit got me back into building gunpla. (The Gunpla is on the cover of my book=) )