I only use a few utility mods, such as Mechjeb (not for the autopilot!!), KAS, and Quantum struts. But I don't use any part packs since I like to keep my ships as stock as possible. As many of them seem to be based off of real life rockets, not KSP rockets. Thus, you end up with way OP parts, such as an SRB that can bring you all the way to orbit.