Gewehr is the German word for a rifle. Previous to the 1840s, rifled guns were not widespread, usually muzzle-loading and termed Büchse, as they are still in German hunting jargon today. Afterwards, Gewehr became the standard term for military-type rifles.
The term "Gewehr" can be encountered in the context of 19th and 20th century military history for nonspecific rifles from German-speaking countries, e.g. in arms trade, in particular for types produced before German unification in 1871.
Specific types, sorted chronologically from 1841 to 1997 and with designer given, are:
References
Gewehr Wikipedia(Text) CC BY-SA