Only one...

[Pterodactylus]

Only ink that stays in rotation all the time, so an easy and obvious choice - Platinum Carbon Black. Because occasionally I suffer from artistic delusions and get out the watercolours; it's the only ink that reliably stays absolutely put in the presence of a wash. And I often write postcards and Cornwall is damp, so it's handy there too. Plus I like it.

Downside to it is it would then restrict what pens I could use, so my not-so-potentially-pen-destroying option would be Pelikan 4001 Turquoise, which is a lovely ink, very reliable, easy to clean, and terribly underrated.

Hey Weevil, how comes that we never saw some of your artworks?
Please post some

[Pterodactylus]

Pelikan Blue-Black is a good choice, but I would choose ESS Registrars Blue-Black.

[grainweevil]

Only ink that stays in rotation all the time, so an easy and obvious choice - Platinum Carbon Black. Because occasionally I suffer from artistic delusions and get out the watercolours; it's the only ink that reliably stays absolutely put in the presence of a wash. And I often write postcards and Cornwall is damp, so it's handy there too. Plus I like it.

Downside to it is it would then restrict what pens I could use, so my not-so-potentially-pen-destroying option would be Pelikan 4001 Turquoise, which is a lovely ink, very reliable, easy to clean, and terribly underrated.

Hey Weevil, how comes that we never saw some of your artworks?
Please post some

Please note the word delusions!

[Paddler]

Assuming that the original poster refers only to fountain pen ink, I would have to go with something bulletproof. After all, if bulletproof is available and relatively inexpensive, why would I choose something else? I would buy a SABLE of Noodler's Legal Lapis.

[Dhruv]

I think we have over 500 bottles of ink now, so choosing one is nigh on impossible. But up there would be Pen & Message “Writing Lab” Old Burgundy.

Definitely, that ink is great. I don't think I have gone through 30ml+ of any ink other than OB, and I do have 400+ bottles of ink.

[top pen]

J Herbin poussiere de lune can't think of any other ink that would come close

[Rossler]

Darn it, that is very limiting, but I would choose KWZ Hunter Green, my favourite since it showed up on my desk.

[RocketRyan]

Still can't decide.

[stevekolt]

Interesting responses...keep 'em coming!

[Chrissy]

I can't choose only one. Sorry. I would be very sad to see Diamine Tchaikovsky disappear forever. However, I'm sure something else would come up that is just as good.

[inklord]

Lately... R&K Salix.

I'll revise that to ... "or R&K Sepia", even if it breaks the rules of the original question!

PS ...and I don't even know what the new R&K SketchInks will do to that scheme (currently waiting for R&K SketchInk "Thea" to be shipped by AP - they held off due to the frigid temps)

[ian1964]

I use a fountain pen for work and Black is the only colour we are allowed to write with, so it would have to be Waterman Intense Black. It is a reliable no nonsense ink that works well in every pen I use.