For Fun Again

Probably Canas just because he's nerd. Red mages are a bit lacking for me. And I don't use them.

i gotta say summer leo because i absolutely adore tobi's art everything they do is amazing and soft

Gameplay-wise:
H!Nowi - flying mage is sooooooo convenient, esp since most of the greens have terrible res, it is so satisfying to see those big numbers.

Character-wise:
Call me simple, I will still vote for B!Tharja for obvious reasons.

So I liked Arvis, and then found out I actually really quite dislike his guts because of him/Sigurd/Dierdre. And his son. (They're too good not to build, though.) My favorites are Sanaki and Lilina, they're a blast to use.

Henry is my favorite red mage because of his character in Awakening.

Celica is my favorite red mage as far as usage.

Oof Red mages, that's probably the hardest for me to think of given that unlike blue or green mages my top 3 of those entire colors would both include at least 2 mages. Meanwhile red is dominated by swords for favorites, doesn't help Fir and Ares are my main and backup merge projects respectively.

But for just red mages I'd have to go in no particular order:

Arvis, tough for me to pass on the ploy and psuedo-healing Emperor and if I needed to use a red mage tank he'd be my go to. Plus bonus points cause I love how they kept the spinning triangle for Valflame, probably one of my favorite weapon animations.

Lilina, I do have a bit of a Binding Blade bias as it's my second favorite game in the series behind only Radiant Dawn. And I mean like her BB counterpart Lilina can absolutely nuke things with her magic. I mean DB6 with Chill Res legendary tome is not something to take lightly damage wise.

SM!Eirika, I have less to say about her but my staple horse team is Ares, SM!Eirika, Camus, and WT!Olwen. So she makes the list because she probably sees the most consistent use of any red mage I have, even if unlike someone like Ares I rarely try to use her outside of a horse team.

Sophia. Totally Sophia!

Lilina
Mainly because of her one-shot nuking potential. Also one of the very few red mages I use frequently.

Winter Tharja
Powerful tank with excellent base kit. Just needs Swap, Iceberg/Glacies and Ward Armor and she's all good to go.

... I don't have too many picks for Red Mages.

Celica, easily. First of all because she's one of my waifus, so there's that. Second, I thought it was clever how they translated Ragnarok from SoV to Heroes. Lastly, and most importantly, I enjoy how versatile and adaptive she is as a unit. She can run offensive or more defensive builds thanks to her weapon. A lot of people underestimate both hers and Tharja's defensive stats imo, they actually have usable defensive bulk to trade hits with DC units unlike other frail mages that'll crumble to anything physical (looking at you, Delthea).

I actually use Leo a fair amount on my cavalry team too, although if I had mage Eirika I'm not sure I'd be using him tbh.

SM Eirika is my best red mage.

Arvis - easily the one I use the most, he's become a core member of my Lunatic Chain Challenge runs.
Lyon - he's a great niche unit and I like using him in AA.
Tharja - I don't use her as much now, but she was the first red mage I used and promoted.