Caladea
Sphinx of black quartz, judge my vow
Jelle Bosma for Microsoft, 2004, and the serif that ships beside Calibri in Office.
Metric-compatible widths first, for the same document-reflow reason as Calibri, and a sturdy low-contrast serif that does not thin out at small sizes.
One entry, because one is the honest answer. A face is listed here only if the substitution would survive a designer looking at both.
Sphinx of black quartz, judge my vow