This tool can transliterate/transcribe text both ways between the Latin script and:

greek: γρεεκ
cyrillic: цыриллиц
devanagari: दएवअनअगअरइ
futhark: ᚠᚢᚦᚨᚱᚲ
hiragana: ひらがな
katakana: カタカナ
hangul: 항울
old italic: 𐌏𐌋𐌃 𐌉𐌕𐌀𐌋𐌉𐌂
gothic: 𐌲𐍉𐌸𐌹𐌺
georgian (mkhedruli): გეორგიან
mtavruli: ᲛᲗᲐᲕᲠᲣᲚᲘ
armenian: արմենիան

ascii (dropping accents, expanding digraphs)
ｆｕｌｌｗｉｄｔｈ
ꜱᴍᴀʟʟᴄᴀᴘꜱ

Unicode Plane 1 mathematical characters:
𝐛𝐨𝐥𝐝, 𝑖𝑡𝑎𝑙𝑖𝑐, 𝒃𝒐𝒍𝒅 𝒊𝒕𝒂𝒍𝒊𝒄, 𝓈𝒸𝓇𝒾𝓅𝓉, 𝓫𝓸𝓵𝓭 𝓼𝓬𝓻𝓲𝓹𝓽, 𝔣𝔯𝔞𝔨𝔱𝔲𝔯, 𝕕𝕠𝕦𝕓𝕝𝕖-𝕤𝕥𝕣𝕦𝕔𝕜,
𝖇𝖔𝖑𝖉 𝖋𝖗𝖆𝖐𝖙𝖚𝖗, 𝗌𝖺𝗇𝗌-𝗌𝖾𝗋𝗂𝖿, 𝘀𝗮𝗻𝘀-𝘀𝗲𝗿𝗶𝗳 𝗯𝗼𝗹𝗱, 𝘴𝘢𝘯𝘴-𝘴𝘦𝘳𝘪𝘧 𝘪𝘵𝘢𝘭𝘪𝘤,
𝙨𝙖𝙣𝙨-𝙨𝙚𝙧𝙞𝙛 𝙗𝙤𝙡𝙙 𝙞𝙩𝙖𝙡𝙞𝙘, 𝚖𝚘𝚗𝚘𝚜𝚙𝚊𝚌𝚎
(beware, many of your recipients may lack fonts necessary to display these)

Enclosed alphanumerics:
circled: ⓒⓘⓡⓒⓛⓔⓓ
parenthesized: ⒫⒜⒭⒠⒩⒯⒣⒠⒮⒤⒵⒠⒟
squared: 🅂🅀🅄🄰🅁🄴🄳
negative circled: 🅝🅔🅖🅐🅣🅘🅥🅔 🅒🅘🅡🅒🅛🅔🅓
negative squared: 🅽🅴🅶🅰🆃🅸🆅🅴 🆂🆀🆄🅰🆁🅴🅳
regional indicators: 🇷🇪🇬🇮🇴🇳🇦🇱 🇮🇳🇩🇮🇨🇦🇹🇴🇷🇸
(since recently, environments tend to show indicators as flags rather than
enclosed letters — support is inconsistent, though)