Common words:
* altar
* collar
* dollar
* guitar
* liar
* polar
* scholar
* sonar
* star
* sugar
* theater
* visitor
Less common words:
* abacus
* acoustics
* adular
* altar
* ambassador
* angular
* apolar
* aviator
* bizarre
* calendar
* cedar
* cellular
* circular
* coplanar
* dinar
* disbar
* embarrass
* extinct
* flamboyant
* granular
* insular
* linear
* lunar
* muscular
* nuclear
* ocular
* popular
* regular
* reticular
* scalar
* solar
* specular
* stellar
* sublunar
* tabular
* turgid
* vascular
* volar
Words with "-ar" as part of a larger suffix:
* -cular: (circular, muscular, ocular)
* -ular: (angular, circular, popular)
* -arly: (regularly, particularly)
* -arian: (librarian, vegetarian)
This list isn't exhaustive, but it provides a good starting point!