HMFoMT and Zoids DS have a huge half-width font and most of it isn't even used (or usable, I tried making a table). Zoids' one even includes a full 8px width joyou kanji set. Also, in FoMT, out of the 8 horizontal pixels only 7 actually show up in-game.
Summon Night Swordcraft Story 3 having duplicate identical text for the boy and girl protagonists even when it doesn't make sense and the scene is identical with the protagonist never being mentioned.
Lufia GBC had English and German as language options, but rather than having separate compression dictionaries for the text (which is further compressed with another scheme) they share the same one for both languages.
In lots of SNES ROMs, they'd compress lots of stuff but the uncompressed player character sprites are stored in a really inefficient way, with huge black areas on the sides that could easily fit the same sprites one more time.
And then there's the games with lower case characters in the font but most (not all) of the main script is in all caps, like Kid Icarus, Metroid, Lunar 1/2 (full font is only really used in Grandia), Taito's Jetsons, Tecmo Secret of the Stars, the French/German versions of Actraiser 1/2 (which even had working lower case accentuated characters), Ganbare Goemon 1's shitty English version, and so many more...