What are some must have mods for KSP?

This comment was posted to reddit on Mar 06, 2015 at 4:47 pm and was deleted within 1 day, 4 hour(s) and 41 minutes.

The most essential mods actually tend to not be the part-mods:

Kerbal Alarm Clock – Helps you avoid time-warping too much, right past your next maneuver node.
Kerbal Engineer Redux – Helps you see each stage's ∆v during construction. Be sure to use a ∆v-map along side this mod.
Precise Node – Because precise maneuver nodes matter.
Transfer Window Planner – Calculates transfer-windows (porkchop plots) so you can plan planet-to-planet ejection burns. Essential for interplanetary missions. Before this mod existed, I was desperate for an in-game porkchop plotter, so when it appeared it was a huge relief.
RCS Build Aid – Essential for building balanced orbiters that translate (and thus dock) smoothly.
Docking Port Alignment Indicator – Self explanatory.

Realism Mods:

Ferram Aerospace Research (FAR) – More realistic aerodynamics. Might be obsolete in KSP 1.0.
Deadly Reentry – Adds reentry heat, heat shields, and death-by-excessive-GForces. Might be obsolete in KSP 1.0.

Later, as you accumulate more mods, particularly part-mods, you'll want these to help make it more manageable:

Active Texture Management – Helps drive down memory usage of textures, which can crash the game if they go unchecked. This is merely for Mac and Windows users. Linux users already have 64-bit support so they won't RAM-crash.
Filter Extensions – Organizes parts in the build-editor in a sane fashion. Basically mandatory if you have a lot of part-mods.
Alternate Resource Panel with OlympicARP Icons – Replaces any conceivable resource-name with a pretty icon. Also has some auto-staging controls. This is increasingly essential as you use mods with many more resources.

Part mods:

Kerbal Attachment System – Winches for building cranes, as well as pipe and strut connections that can be built by astronauts on-site. Essential for ground-bases or transferring fuel without docking ports.
ScanSat – Offers remote sensing, which lets you choose better landing sites, as well as interacts with resource mods like Karbonite.
Procedural Parts – Lets you make fuel-tanks of various shapes, like rounded cylinders, arbitrary radius/length cylinders, cones, rounded cones, etc. And the texture of each tank can be customized too. I strongly recommend adding JebediahKerman42's texture-pack alongside this mod. Very handy.
Procedural Farings – Farings are almost mandatory if you use FAR. And these farings are the most flexible. This mod will likely become obsolete in KSP 1.0.
B9 Procedural Parts – A more customizable flavor of procedural wing.
Adjustable Landing Gear – Good for getting a wider wheel-base for stability, while still attaching the wheels to the fuselage rather than putting them on wings. Also allows for control of the springiness of the gear, significantly improving landings if used right).
Karbonite – Because in-situ sustainability matters. This mod might become obsolete in KSP 1.0 (not sure).
kOS – Essential for people who can program (not for everyone!). I use this for 90% of my orbital maneuvers, and combined with Precise Node, all my maneuvers are incredibly accurate, easy, and doesn't feel like cheating since I had to code the scripts.

There are many, many more part mods. These are just the ones I