Broken text
Unicode has marks that stack above and below letters, letters from other alphabets that look the same, and blocks in every shade of grey. With those you can break a text and it's still text: copy it and paste it anywhere.
Zalgo
Marks piling up above and below every letter.
g̻̹̠͎̮̰ͩ̀̽̏̅ͣl̰i͎̼ͦ̏̉̇̉ͦţ̨̡̮̗̗̻ͬ͛̇c̰͎̯̣̮̠̄ͦͪ̇̃h͉̻̪̪̩̊ͦ̀̂̔͋
Blocks
Letters turning into █ ▓ ▒ ░.
▒░itch
Homoglyphs
Greek and Cyrillic letters that look Latin (and aren't).
ցӏιтcɦ
Mojibake
UTF-8 text read as if it were Latin-1, like old emails.
glitch
Strikethrough
A line through every letter, with the odd underline.
g̶̲l̶i̶̸t̶c̶h̶
Upside down
Flipped over and right to left.
ɥɔʇᴉlƃ
Full width
The wide letters of Japanese keyboards, with the odd gap.
glitch
All mixed up
A bit of everything, letter by letter.
gĺ̷̙͆̀itch