As far as I know, the one you should NEVER inactivate is Lucida Grande if you want your system to keep going! Otherwise, Helvetica and Helvetica New are also needed by some apps.
Did you try it? Because here is what I read on their download page:
Pushkin - new free font to download.
This font is based on the handwriting of Pushkin.
It contains the Russian and Latin letters, as well as Puskin's initials and signature
I've found one called Pushkin there :
http://www.paratype.ru/shop/default.asp?Item=FREE&page=free/default.asp
Hoping it's what you were searching for...
Regards ::angel::