The modern, refined version of the classic Helvetica.

Very early keynotes (iMac G3, iPod classic) used a custom version of – a slightly modified Myriad Semi-extended. This was Apple’s corporate font for print and packaging.

If you watch keynotes from Steve Jobs (iPhone 1, MacBook Air envelope) or early Tim Cook (iPhone 5, iPhone 6), the font was (usually Light or Ultralight for headlines, Regular for text).