>Create new constellations/fill up your museum
>Make a perfect town (not that hard really)
>Design some cool patterns or look online for pre-made ones, of course if you do that you'll have to reference the pre-made one to make it on your game. Kinda tedious but fun after its finished. Here's a good site
http://www.animalcrossingcommunity.com/patterns.asp
>Get complete sets of furniture for each of your rooms, or mix it up however you like
>Pay off all your debt without cheating
>Trap your neighbors by digging holes around them
>Get all the pitfalls from Booker and push your neighbors into them, or surround them in pitfalls and watch as they helplessly flop about
>Send mail to your neighbors with junk attached and you may get something good in return