Unifont is a Unicode font with a glyph for every visible Unicode Basic Multilingual Plane code point and more, with supporting utilities to modify the font. The Unicode Basic Multilingual Plane covers the first 65,536 (or 2^16) Unicode code points.
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Pro Unicode support
This font covers the entire BMP and work is still being done to expand it even further.
Con The zero character is not sufficiently distinguished from the capital "O" character
Especially for programming, zero characters should have slashes to make them distinct from other circular or oval characters.