MC Command Center is the only mod I refuse to play without.
I use LittleMsSam's mods pretty often. I love her "Personal Objects" mod especially. Personal objects lets you set certain objects as just belonging to 1 specific sim. I always have 1 sim who paints and 1 who plays music, and I always hate when everyone else in the household who I don't even particularly want gaining those skills randomly decide to start painting or playing an instrument. Guest sims to the house also randomly decide to start playing instruments sometimes. Her mod also lets sims claim computers, video game consoles, tv's, toilets, sinks, tubs and showers, tablets, stereos, among other things as belonging to them.
I also love chingyu's More CAS Traits for Sims Mod (& For Pets!) mod.