Wow! this is one charm I think everyone can get behind. All three modes are sooooo good in constructed!
1) 4 damage to target player? for two mana? Yes please. How insane is that? I think even regular mono-red decks will splash white via Sacred Foundry and Clifftop Retreat to go out of their way in order to play this burn.
Note: it will however not save your planeswalkers from dying to unblocked attackers.
Bonus: Play it in commander with something like obliterate and watch your opponents cry!
3) Double strike? Double Cleave? Slap that on an unblocked creature and double your damage output. It can be pretty insane with any creature ability that triggers via combat damage or a creature that has something Ciphered on it as well.
Which mode will you choose?
All 3 modes make you want to run 4 maindeck in any Boros deck and quite possibly Naya decks. It keeps the aggro going at all times. In Commander, I would again consider this in my Gisela deck. I can tutor it up with Sunforger and effectively ‘Negate‘ a Wrath of God -style effect. I probably won’t be choosing the other two options much.
Well, the 4 damage ability usually makes quick work of a few early planeswalkers.
Burn spells are generally half as effective in Commander due to the fact that players start at 40 life. In this context, red decks are generally disadvantaged and also less popular. Aside from burn damage, Chaos Warp is probably on of the few red spells to deal with planeswalkers. Including this in your 100-card deck will give you some unexpected range.
In those Magical Christmas land situations, you can always cast this targeting your Gisela and bring your opponent 1 damage short of losing to Commander damage. We can always dream right?