I think it’s just “dot”, quite distinct from “period”(.)
The “dot accent” used in some languages (eg Polish over z) is the exact same dot.

pub quiz answer is “tittle”

Si

That answer’s a bit too titillating sii

i thought tittle was the cross on the t and jot the dot on the i.

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edit
seems sii was right! tittle

According to Adam Twardoch’s diacritics howto, I think it should be called “kropka”. I know that’s technically the name of the polish diacritic, but typographically it’s exactly the same as the dot on the i, so why not?

semper ex typophile aliquod novi, sorry to mix languages.
Tim

Although what Paul says sounds familiar, looks like OED agrees with Si (see 1b):

tittle, n.
1. A small stroke or point in writing or printing. a. Orig. rendering L. apex ‘point, tip’, applied in classical L. to any minute point or part of a letter, also to the mark over a long vowel, as á, later also to a line indicating an abbreviation. More recently applied also to the Spanish tilde or circumflex over ñ, formerly to the cedilla under ç. By extension, any stroke or tick with a pen.
b. The dot over the letter i; a punctuation mark; a diacritic point over a letter; any one of the Hebrew and Arabic vowel-points and accents; also, a pip on dice.
†c. A name for the (usually) three dots, following the letters and contractions, in the alphabet on horn-books, where it is usually followed by Est Amen; so that tittle est Amen came to be used for ‘the end or conclusion’. Obs.

etc...

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Ever since I chose to block pop-ups, my toaster’s stopped working.

Great!

I think it should be called the i ball.