What is your favorite thing to do in the game? and what packs help that?

My favorite thing lately has been Rags to Riches challenges, and Eco Living has been an absolute godsend for those. Doing a Dumpster R2R is so much fun, and the Community Spaces are great ways to help out your Sims who can't afford to buy crafting items yet. Nifty Knitting and Paranormal also help out a lot too - not only with the knitting and the treats the spectres leave, but also with Plopsy.