There's a prowess deck growing in Standard (and other formats), and this is its two-drop.
Emberheart Challenger1R
Creature — Mouse Warrior (Rare)
Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.) Valiant — Whenever Emberheart Challenger becomes the target of a spell or ability you control for the first time each turn, exile the top card of your library. You may play that card until end of turn.
2/2
I don't know entirely HOW viable it would be at this point since I haven't played Standard in many moons, but I feel like the bones of a decent RW aggro mouse deck are definitely there post-rotation.
There's a prowess deck growing in Standard (and other formats), and this is its two-drop.
Emberheart Challenger1R
Creature — Mouse Warrior (Rare)
Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.) Valiant — Whenever Emberheart Challenger becomes the target of a spell or ability you control for the first time each turn, exile the top card of your library. You may play that card until end of turn.
2/2
Emberheart Challenger 1R
Creature — Mouse Warrior (Rare)
Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Valiant — Whenever Emberheart Challenger becomes the target of a spell or ability you control for the first time each turn, exile the top card of your library. You may play that card until end of turn.
2/2
Slickshot Show-off may beg to differ, or share the deck with the little mouse. There's plenty of good stuff right now on Izzet Prowess that maay get a shot once The Wandering Emperor or Wedding Announcement rotate out, but losing Spell Pierce and Kumano faces Kakkazan can be an issue.