Some are guaranteed in a particular product, whereas others are only obtainable through some special promotion
For example, in Urza's Destiny (the set where I was the entire design team), there were two different cycles that explored effects that scaled based on how many cards of a certain color were in your hand
Yukoku no Moriarty (Moriarty the Patriot) Seinen Akebi-chan no Sailor-fuku - Akebi's Sailor Uniform Akira Alice-san Chi no Iroribata (Arisu Sanchi No Irori Atelier of Witch Hat (Tongari Boshi no Atorie) Azumanga Daio Berserk Blue Period Bocchi the Rock
Since the start of the year, Bulbasaur has been planted firmly between $9 and $12, and even a massive buyout on July 19 (when the average number of copies per buyer rose to 25.8) couldnt uproot it
If your favorite MTG creature type is badly represented or doesnt have enough good cards to make a typal deck, dont worry
The low mana cost of Shadowspear is what makes this card such a good answer: the equipment itself is just 1cmc and the ability -- which doesn't even need you to equip first to use -- is also 1 mana, making it super easy to tutor up and use it when combined with follow-up removal