Just as the title says, activities or hobbies that can become quite strange and shady which most of them will seem quite annoying to you, that's because of taking things to the extreme without measuring the consequences, let's start:
How about Disney?
Yes the famous empire that has a city of its own, has something really dark and it is not precisely the company, but the obsession of some people with objects of this powerful franchise, the pins exchanges, there is a black/gray market in all this matter, where they seek to obtain rare and scarce pins, but where is the murky, because people seek to exchange the pins, some will show up with counterfeit pins, or try to sell them to you and even try to change the Disney staff to get legitimate ones. This scenario is repeated in other activities such as Olympic pins, to give another example. It is quite a lucrative market do the search on any trading site like ebay or amazon.
Yu gi oh, MTG, in the case of card games, in tournaments the effects of some of the cards looking for some really uncomfortable situation to the point of being disgusting, in Yu gi oh for example there is a card called "The card is Yu-Jo Friendship" which forces you to give the hand to the opponent, this is used to smear the hand in private parts, armpits in which previously sought total lack of hygiene to make it as disgusting as possible.
All with the purpose of making the rival abandon the game and lose the tournament. The end justifies the means?
Beekeeping
If growing bees, what's so strange and obscure about it? There are other beekeepers who will seek to poison the hives of others, it is even said that there are armed diseases to decimate the hives.
Macrophotography
Even in Hive, these cases have been seen, there are people who in order to take excellent pictures of insects kill the insects so that they are immobile and can take pictures at different angles, how do they do it? Some freeze them that way they do not need to crush them, so when you see photos of insects look at them well, compare the photos of how their legs and eyes look and compare it with another of the same species.
Maybe some of the facts you knew, others you had no idea what really happened, I hope you enjoyed the reading.