I believe that one of answers already given should be accepted, since all of them are succinct, complete and correct. Still, I want to mention a couple of other examples, so, there's a word владыко
which is vocative of "владыка". It's used to address higher ranks church officials, so domain of usage is pretty tiny. In fact, in Russian is extinct to that level that de-facto "владыко" is treated quite often as a word of it's own.
The same happened with, for example, человече
, which used to be vocative for человек
. Sometimes (again, very rarely) it's used to make speech sound archaic, most likely in ironical way:
Все, что вдохновляет господ поэтов, было рассыпано вокруг него
щедрою рукою в огромном количестве и, казалось, говорило и пело:
"На, бери, человече! Наслаждайся, пока еще не явилась осень!"
Here the author (Anton Pavlovich Chekhov actually) uses человече
correctly, as a vocative.
And here modern author is using (just to sound a bit more pathetic) it incorrectly, as a nominative:
Когда звучит это фраза на всех языках мира, становится ясно -
человече её изрек после тяжелого испытания.
Other form worth to mention is друже
(from друг
), like in phrase "И как же нам, друже, Совесть заставить улечься?".
To conclude, one thing you should know about any old-form vocative usage in Russian - all such words are rare and extremely bookish. Not even everyone will recognize what you are saying if you'll actually use them.