.htaccess - Friendly URLs with special characters

Possible Solution

RewriteRule ^usuario\/([a-z,0-9,A-Z,._@:=!\?-]+)?$ index.php?pg=usuarios&usuario=$1

Notes

• [] works as a catch per scan, "in the character I'm testing, do I accept what possibilities?"
• Note that you only need the character once for it to be accepted, so , does not need to appear several times - although I believe its intent was to separate contents
• In regex there is no need to separate content, it simply follows the last sequence a-z,0-9,A-Z, = a-z0-9A-Z
• Special characters can be literally taken through escape \ , \? , \+
• Within [] you have two means of capturing literally - having in mind that it is also a special character (from, to), holding it at the end -] or applying escape \-

Improvement

• Note that in the brackets you have a-zA-Z0-9_ which is just the anchor \w

Improved solution

RewriteRule ^usuario\/([\w,.@:=!\?-]+)?$ index.php?pg=usuarios&usuario=$1