I have a highly subjective, pseudo-realism pack that I've put together that I like. It's massive, but doesn't add too much in the way of parts. Most are plugins. The added parts are mostly B9 Aerospace, even though I don't do much in space planes. I like the possibility and to experiment with space planes, and I feel the plane parts are somewhat lacking. B9 does a little overkill on additional parts to compensate, but I like the options that are even flexible enough to use with conventional rockets. Realism or not... Must-haves: Crew Manifest (Docked ships should be able to transfer crew) Kerbal Joint Reinforcement (Excessive strutting is silly, imo) MechJeb2 (I know this one is controversial. I mostly use it for the orbital data, but I made it a point to do everything it does for me manually at least once. My time is valuable, but I still like hard-earned accomplishments.) ModuleManager (I'm a big fan of custom configs to give added parts to the tech tree, and Mechjeb to every pod with a few lines of code.) PreciseNode (Quicker and more intuitive than MechJeb's Maneuver Node Editor) Protractor (For when I want to do transfers without MJ. I use it to backup MJ, as well.) Chatterer (It's too lonely for me when it's quiet.) RCSBuildAid (Invaluable) LazorDockingCam (for the cam while docking) Docking Port Alignment Indicator (for more docking attitude details) SelectRoot (Subassembly made easier) KerbalAlarmClock (Slightly faster than MJ Auto-Warp, and I use it for SOI transitions so my orbits don't shift) Minus the above, a comprehensive list: AviationLights B9 Aerospace PartCatalog (Highly Recommended) RemoteTech (Highly Recommended) Ion Engine Sounds RCS Sounds New Sounds Procedural Dynamics Procedural Fairings (Highly Recommended) Editor Extensions (Highly Recommended) Life Support Mod Vertical Velocity Control Deadly Reentry Enhanced Nav Ball (Highly Recommended) Visual Enhancements (Highly Recommended) KAS (Highly Recommended) FAR (Highly Recommended) All of these combined, provide for a reasonable collaboration between realism and play-ability.