Â

From Teflpedia

 (A-circumflex, lower case â) is the letter A with a circumflex diacritic.

In English, it's generally only used in French loanwords, such as château or gâteau. Note that the circumflex accent is indicative of historical elision of the letter S, and this may be important for cognate recognition. So, e.g. French "château" is a cognate with English "castle".