Textlicious

Textlicious is a tiny extension that lets you enter styled text in places that normally accept only plain text. Make your tweets more expressive, your texts stand out, and your posts on the ‘book the envy of all your friends.

Just highlight any text you’re typing in any app on your iPhone or iPad, click on the “Share” menu item, select the style you want from Textlicious, and paste the newly styled text over your old word.

Available styles include bold, italic, serifed, typewriter, script, double-struck, and more.