If you target markets where the native language is not English, you are likely to encounter letters which are not part of the standard Latin character set. It is immediately obvious for languages such as Japanese or Arabic but common as well in French, German, Swedish, etc…
You may be tempted to consider buying IDN (Internationalised Domain Names), which allow characters not part of the ASCII set.
Be aware that usually buyers are not that excited by such names.
While the implementation and support of IDN dates back from 2003, those
names never really took off and as such as an investment may take a
long time to materialise.
So unless you have enough experience and know potential buyers who already expressed an interest in IDN, I would recommend you stay clear of them.