ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÑÒÓÔÕÖÙÚÛÜßàáâãäåæçèéêëìíîïñòóôõöùúûüŒœ¿«»

This is the complete list, I think, they may not be necessary for all languages though, this list does not include APAC (had to break the lines, the string of them was too long):

ÀÁÂÃÄÅĀĄĂÆÇĆČĈĊĎĐÈÉÊËĒĘĚĔĖĜĞĠĢĤĦ
ÌÍÎÏĪĨĬĮİIJĴĶŁĽĹĻĿÑŃŇŅŊÒÓÔÕÖØŌŐŎ
ŒŔŘŖŚŠŞŜŤŢŦÙÚÛÜŪŮŰŬŨŲŴÝŶŸŹŽŻ

àáâãäåāąăæçćčĉċďđèéêëēęěĕėƒĝğġģĥħ
ìíîïīĩĭįıijĵķĸłľĺļŀñńňņʼnŋòóôõöøōőŏ
œŕřŗśšşŝťţŧùúûüūůűŭũųŵýÿŷžżź

ÞþßſÐðŒœ¿«»

if you’re translating just for Spanish, you should be ok with these characters: ÁáÉéÍíÓóÚúÑñ¿

Also, these two are commonly used in copy: ©®™

If you’re QAing a piece that should be localization-ready, it’s a good idea to paste the above characters into the xml and make sure they all render properly.

• If testing Cyrillic: абвгдежзийклмнопрстуфхцчшщъыьэюяёАБВГДЕЖЗИЙКЛМУФХЦЧШЩЪЫЬЭЮЯ
• If testing Korean: 검사하다
• If testing Japanese: テスト 試験 検査
• If testing Chinese: 进行测验 進行測驗
• If smart – test all three at the same time: 검사하다 – テスト 試験 検査 – 进行测验 進行測驗
• I believe this is the turkish alphabet (note these are only caps): ABCÇDEFGĞHIİJKLMNOÖPRSŞTUÜVYZ