It reduces the mana cost of creature spells of the chosen type by 1 and gives you a chance at the beginning of your upkeep to look at the top card of your library and draw it if its a creature of the chosen type
The closest I could find to anybody doing it in the mainstream recently was Artifact (I know, I know, I'm stretching the word "mainstream" here) with a slightly bastardised version of the concept handled via Steam's marketplace, and even then it's still an online auction house, not just doing fun swaps with your pals and saying "well I've got this, what've you got?", like exchanging the best parts of your packed lunches at school
Syr Ginger, the Meal Ender I think this newly printed two-drop 3/1 on curve Food Knight with three key abilities if any foe has a planeswalker
While this technically doesnt leave tons of room to make your money back, value isnt really a concern for these drops
Palkia ex : This legendary Water deck uses Palkia and energy generation to hit all enemies at once