In my headcanon, Twilight was never Celestia’s student, and thus never became an Alicorn. She instead became best Friends with Starlight at an early age. I rewrote all 3 of these ponies so that their fates are actually in the meaning of their names.
 
Twilight: Between Day and Night, Light and Darkness. Her actions will determine the path she will walk. (???)  
Starlight: A beacon of light, glimmering like a star in the dark night sky. (good)  
Sunset: As the sun sets, giving way to darkness, her light fades away, and she is consumed by darkness. (evil)

No, no, wait…
 
JETFIRE! XD

Fog Lamp. :P

Cloud Glitter? Idek XD

Cloud Burst? :3

On one hand, Starlight has an obvious snowclone name that marks her as a villainous foil to Twilight.
 
On the other hand, she’s the best-executed villainous foil that Twilight has had so far, so she earns it.

ALL SHINIES UNITE!

Even with this I’m bad at coming up with names! XD

Stratosphere Resplendant

…
 
Guess mine counts

DUSK DAZZLE
 
…
 
Wait, that sounds familiar…

Not just sky, night sky.
 
@Background Pony #DFC9  
DAWN HAZE!
 
(I’m a rebel.)

@Background Pony #9124  
Swirl is not a shiny name. Dusk Twinkle.

Surprised no one has mentioned Star Swirl.

@aHappyRobot  
Really, who else could it be for that? I’ve got nothing but love for the kid, but I don’t think I’d eat her cooking even as a means of attempting suicide.

@Scrounge  
XD perfect!

@aHappyRobot  
Sweetie Belle.

Does this mean Trixie is now kicked-out of the “Magical Trio?”

@Scrounge
 
Good point! Come to think of it Hugh Jelly from that episode would work well for touch. Not sure what to do for taste though…

@aHappyRobot  
Well, there’s already a pony who’s too smelly.  

If I wanted to trademark the name ‘Midday Brightness’, I wonder if Hasbro would have already beaten me to the punch.

@Scrounge
 
lol, now all we need is 3 more annoying ponies for the other senses so we can create THE IRK SQUAD!

plot twist: they’re all long lost sisters.

@aHappyRobot  
Only if you don’t count Klaxon Shrill.