You will not find some types of business which are nevertheless capable to become very profitable business in the all-Russian qualifier of types of economic activity.
Often such business is as though hobby continuation, but already on a commercial basis. You, for example, very successfully write for friends and acquaintances of the poem to order. Why to this hobby not to become business? And if you like to cook, why to you not to offer the services to firm, and not to earn on preparation of dinners for her employees?
Yes it can be everything, everything! Mini-nursery for a certain species of animals, выгул dogs at neighbors, repair of old books at bibliophiles and the other, other other …
And how to be with ОКВЭД? – you ask. It is very simple. If you by all means want to be registered as the businessman, you have the right to appropriate to the activity a code and to place it in the section "Miscellaneous". For the rest any distinctions with the person who conducts quite standard activity, does not exist.
However, registration of the businessman is not obligatory. If to take, for example, the organization of mini-nursery Siamese, say, cats – the law does not consider this sort of activity by means of receiving profit.
So to be registered or not – depends only on you. However, useful after all will consult in this respect in tax inspection.