Rewrite a card from early Magic (Alpha through, say, Ice Age) following the modern Magic design style (modern color pie, stronger creatures, weaker non-creatures) and the suggestions given by Mark Rosewater in his Starting Over article.
So:
1) Instant as a supertype - all Instants are Instant Sorceries instead;
2) Artifacts and enchantments would have more mechanical distinction, with enchantments getting all global effects, and artifacts getting one time use effects, and once per turn activation effects;
3) More definition between creature types;
4) Sub-types for non-creatures (Fire spells get a Fire subtype);
5) Legendary as an upside mechanic instead of a downside;
6) Get the beginning phase shortened to two steps;
7) Spells don't fizzle if their target is removed;
8) Milling as 'Discard from library'.
Example:
Blue Elemental Blast1U
Instant Sorcery — Elemental Water
Choose one —
• Counter target red spell.
• Return target red permanent to its owner's hand.
So:
1) Instant as a supertype - all Instants are Instant Sorceries instead;
2) Artifacts and enchantments would have more mechanical distinction, with enchantments getting all global effects, and artifacts getting one time use effects, and once per turn activation effects;
3) More definition between creature types;
4) Sub-types for non-creatures (Fire spells get a Fire subtype);
5) Legendary as an upside mechanic instead of a downside;
6) Get the beginning phase shortened to two steps;
7) Spells don't fizzle if their target is removed;
8) Milling as 'Discard from library'.
Example:
Blue Elemental Blast 1U
Instant Sorcery — Elemental Water
Choose one —
• Counter target red spell.
• Return target red permanent to its owner's hand.
Next: Channel