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 SwatImp's MischiefThinking about putting together a Jund hard control shell with these counterspells.