Off the top of my head for portraits:
I find it interesting in general that the men suffer way more clothing damage in their under-10 portraits than the ladies, culminating in Chrono-Ranger's ending up shirtless which I can't say I mind in the slightest.
Bonus points though for original Parse who as near as I can tell suffers naught but some dainty cracks in her glasses.
I really like AZ and Bunker's Termi-Nation portraits, as we rarely get to see either of their faces and they're more visible in these looks.
Freedom Five Tachyon is wicked awesome. Her entire facial expression and pose just exudes attitude and "I'm the badass in town and don't you forget it".
Freedom Five Wraith's incap gets points for how melodramatic it is, stylishly hiding her face.
Visionary Unleashed's incap is so pretty and serene looking.
Dark Conductor Argent Adept's under-10 portrait is one of the downright freakiest things in the game and I love it.
As for cutscene messages:
Freedom Six Bunker and Fright Train's nemesis messages are utterly hilarious; basically them going "WTF?" "WTF?" at each other with train puns (and is basically 100% of the reason I hope we get special messages for the OblivAeon heroes and their normal selves).
Prime Wardens Argent Adept and Akash'Bhuta is pretty much a mutual Badass Awesome Boast deal.
Just about every single Captain Cosmic and Infinitor message makes me weepy-eyed for how sweet they are. XTREME Cosmic and Infinitor in particular is surprisingly sweet considering the source.
XTREME Cosmic's normal message, on the other hand, is just downright hilarious.
Finally, Freedom Five AZ and Team Miss Info is also really sweet for AZ calling the F5 his family.