Imagine I cast a Rampant Growth and I haven't altered the order of the top of my library in any way. Then, because I don't want to go through my whole library, I reveal the first card of my library (which supposedly is in a random order) and it is the land I was going to search for. Can I put it in play and don't shuffle my library?
Theoretically speaking the cards below that land are in a random order and I have no information about what I'm going to draw next. Technically speaking there shouldn't be a problem with this, right? But, is it legal?
The rules of the card say "Shuffle your Library" not "randomize your deck". You're expected to follow all of the instruction of the card as written, as such, a shuffle is required.
So, no, not legal. There's probably stronger supporting evidence for this, but you could also search the forums to find them as this question has been asked many times before.
If doing so is fine by you and your opponent, it's fine. But technically it is not following the rules. And there are specific situations where it would change the outcome.
Specifically, you are avoiding searching (by simply revealing), and you are avoiding shuffling, so any effects that interact with these actions would be impacted.
Theoretically speaking the cards below that land are in a random order and I have no information about what I'm going to draw next. Technically speaking there shouldn't be a problem with this, right? But, is it legal?
My Peasant Cube - CubeCobra
So, no, not legal. There's probably stronger supporting evidence for this, but you could also search the forums to find them as this question has been asked many times before.
Specifically, you are avoiding searching (by simply revealing), and you are avoiding shuffling, so any effects that interact with these actions would be impacted.
Cosi's Trickster
Psychic Surgery
Ob Nixilis, Unshackled
Mindlock Orb