Re: Basic GURPS Toolkit?
 

My typical GURPS Toolkit includes the following for all campaigns:

Basic Set: Characters
Basic Set: Campaigns
Power-Ups 2: Perks
Power-Ups 3: Talents
Martial Arts
and my homebrew Power-Downs 1: Quirks, usually for reference

From there, it breaks down by genre:

Fantasy settings:
Low-Tech
Magic
Thaumatology
Dungeon Fantasy 1: Adventurers (for the templates; I don't dungeon-crawl)
Dungeon Fantasy 5: Allies
Dungeon Fantasy 9: Summoners
Low-Tech: Instant Armor

Space Opera:
Ultra-Tech
Powers
Psionic Powers
Space
Spaceships
Spaceships 4: Fighters, Carriers, and Mecha
Spaceships 7: Divergent and Paranormal Tech
Gun-Fu
Power-Ups 5: Impulse Buys
Bio-Tech

Super-Hero: (in no real order)
Powers
Supers
Psionic Powers
Thaumatology
Low-Tech
High-Tech
Ultra-Tech
Bio-Tech
Gun-Fu
Power-Ups 1: Imbuements
Power-Ups 4: Enhancements
Power-Ups 5: Impulse Buys
Psi-Tech
Spaceships
Spaceships 4: Fighters, Carriers, and Mecha
Spaceships 7: Divergent and Paranormal Tech
Pyramid 3/34: Alternate GURPS

Monster/Vampire Hunters:
High-Tech
Ultra-Tech (for the occasional TL9 hardware)
Thaumatology
Thaumatology: Ritual Path Magic


I also keep Social Engineering and Social Engineering: Pulling Rank on hand for a lot of stuff, but wouldn't count them as part of my usual "toolkit".

Re: Basic GURPS Toolkit?
 

All campaigns
Basic Set, both books
Relevant Tech-book
Martial Arts
Horror

Sci-Fi/Space
Traveller: Interstellar Wars, which I adore for it's spaceship system (the Spaceship series never appealed to me)
Space

Fantasy
Low-Tech Companions 1-3 (mostly just the 3rd, actually)
Magic
Thaumatology

It's always nice to have Powers near for when I need those extra modifiers, as well as the Power-Ups series. Bio-Tech is on my wishlist, and Social Engineering is always lurking in the back of my head, even though I rarely refer to it.

Re: Basic GURPS Toolkit?
 

GURPS Lite: most of the rules I need are inside!

GURPS GM's screen: a very useful tool to find what is not in GURPS Lite during the game (Hit location table, Fright Check table, Critical Success and Failure tables...) but also during character generation, thanks to the booklet Character Creation sold with the GM's Screen (a complete list of advantages, disadvantages and skills - with all the required data for skills).

GURPS Basic Set: for all what I cannot found in GURPS Lite or GURPS GM's Screen.

That's all what I need on my GM's table...

During preparation or player character generation, I sometimes glance at High Tech, Magic or Martial Arts. But, for me, these are add-on, not basic toolkit.

Re: Basic GURPS Toolkit?
 

For me it's

Basic set
Gm screen
Skill categories (to ease character generation)

I just became aware of and am loving rpm so if magic is involved then the rpm book

I can't honestly think of anything I couldn't do with that combo.

Genre specific books make stuff allot easier/faster, add flavor, and generally help fully flesh out the world in a way that can be hard to do from scratch, but aren't necessary so long as you have the genre/setting already firmly in mind.

Re: Basic GURPS Toolkit?
 

Aside from the basic set I think that the tech books have probably seen the most use in my campaigns.

Aside from acting as a source of gear I find that they actually help me to visualise the worlds that I am building Not to mention inspiring a number of plots.

Other than the tech books, the most useful books for the kind of campaigns that I run these days (mostly low fantasy or space opera-ish) have been fantasy, thaumaturgy, space and (oddly given that I hate the setting) infinite worlds. Aside from thaumaturgy which mostly just there to give me the magic system I want rather than the one inherited from earlier editions this is as much for their 'off label' uses.

These books contain a number of good general world/setting building tools. IW for example offers an improved treatment of the basic list of government types, an annotated list of cultures and the 'social gageteering' rules. Ok a lot of this stuff is probably redundant post social engineering (which I have to admit that I still don't own) but I was using these first and I am more than happy with the results.

Re: Basic GURPS Toolkit?
 

Characters
Campaigns
Powers
Martial Arts
Whatever Tech book applies to my campaign.

My homebrew magic system drew heavily from Thaumatology but I don't actively use the book.

Spaceships 1-? are part of the backbone of my Space theatre.

I encourage use of PU2 and PU4 and the Skill categories hand-out in character creation.

And, I requently use Action 2 and the GM screen as resources.

Re: Basic GURPS Toolkit?
 

GURPS Lite, GURPS DF 1-3, GURPS Magic, GURPS Skill Categories, and GURPS Basic Set (lightly used when called upon).