Best off-colour effects

[Aetherium Slinky]

I'm interested in learning about cards that have a strong effect in one colour and are rarer in other colours. I'm personally most invested in counterspells but can you suggest any other cool off-colour effects that could make a shell for something interesting? Preferably not just one-offs.

For counterspells I have thus far collected:
Red Elemental Blast, Pyroblast, Tibalt's Trickery, Deflecting Swat
Imp's Mischief
Thinking about putting together a Jund hard control shell with these counterspells.

[Landale]

Guttural Response, Deathgrip, Lifeforce, and Withering Boon are some other decent counter options outside of blue.

[The Golgari Guy]

There's a reason why Veil of Summer is sometimes called the "one mana Cryptic Command"

[WWolfe]

White has Mana Tithe, Dawn Charm, Lapse of Certainty, and Rebuff the Wicked.

Black has Dash Hopes & Withering Boon.

[Eryx92]

Order of the Sacred Torch is also quite interesting.

[anjinsan]

Burnout is narrower than its counterparts but also cantrips, which is obviously pretty nice.

I'm pretty sure there's a colour-bending deck in the likes of Lifeforce and Reap if combined with stuff like Painter's Servant. Sadly Darkest Hour is only creatures but would work with, say, Nature's Wrath plus Urborg, Tomb of Yawgmoth.

[trophius]

Temporal Extortion is a fun black extra turn spell XD

[Bonethousand]

Temporal Extortion is a fun black extra turn spell XD

There's gotta be some sort of Abzan stax build with this card and Yasharn effects, right?

[Aetherium Slinky]

Temporal Extortion is a fun black extra turn spell XD

There's gotta be some sort of Abzan stax build with this card and Yasharn effects, right?

I highly doubt being able to cast this thing in Abzan. Even two colours would pose problems. I had an UW deck that tried to cast Mind Over Matter which wasn't easy.

[Morganator 2.0]

Temporal Extortion is a fun black extra turn spell XD

There's gotta be some sort of Abzan stax build with this card and Yasharn effects, right?

If there isn't already, you can be the first to try and make one.

[Bonethousand]

Temporal Extortion is a fun black extra turn spell XD

There's gotta be some sort of Abzan stax build with this card and Yasharn effects, right?

If there isn't already, you can be the first to try and make one.

Update: I failed, but I did start making a Tayam, Luminous Enigma humans aggro/stax nightmare that I feel like has some potential, but mostly doesn't know what it's doing.

I hate that I want to try.