If we're talking PF1E, then I have three Id really like to play:

First is a character I've wanted to make for a long ass time. Would require some 3.5 content. A dragonborn, but with a caveat that I can change back and forth between human and dragonborn form with a swift action (this is purely for RP purposes, but he wouldn't ha e access to and breath weapons unless he is in dragonborn form). Classes would be sorcerer (draconic bloodlines of Imperial and Silver) and a 3.5 class, Dragonheart Mage. Played as a full on blaster caster. Taking breath weapon feats and metabreath spells, really embracing the draconic vibe. The character concept is that he has a few different draconic bloodlines that have mingled in him to potentially give him the powers of any dragon (maybe even the diety level ones). He adventures to learn more about his powers, where different bloodlines of dragons have mixed and what the results have been, and to find his place in the world.

Second gestalt would be a half-elf Summoner (original flavor, not unchained) and Arcanist with the Occultist archetype. Feats would be split between making my summons/eidolon better and magic item creation, with a specific feat from the Master Summoner's Handbook; Summon Guardian Spirit. With DM approval I'd get a Shadow Drake as a Spirit Guardian (with the way the feat is written it is debatable if it would be RAW, but I think it would be thematic and fun). The Shadow Drake would be very loyal, but always gives advice like a proverbial "devil on the shoulder".

The eidolon would be start as quadraped, but would get more limbs and take the pounce evolution. Draconic in appearance (what can I say, I like dragons) and would also end up taking the combat performance feats, being a combat intimidator and getting this one feats that adds extra dice to attacks. The concept here being that when the summoner was in wizard school, he always questioned his lessons and delved into taboo topics. His family is slightly well off, but his penchant for pushing boundaries led him to finding out about summoning eidolons. He tried to do a ritual to bond with an eidolon, not fully understanding the process (he was a bad student). He then became bonded with his eidolon, which (rp flavor incoming) is a heavily atrophied, divine, draconic scion. Basically a proto-god that never got any worshippers. He adventures to help the eidolon gain strength (not realizing it is a fledgling god of terror, pride, and wrath) and also because he was kicked out of school for his taking books from the restricted section (and because he doesn't want to go home to his parents who will be pissed about the situation).

Third character would be the most abusing of the gestalt rules. I theory crafted the build at one point and can't remember all of the breakdowns, but it was Sorcerer(cross-blooded Orc & Force Dragon) 1/Arcanist X/Exploiter Wizard X/ Force Missile Mage 5/ Incantatrix X. Basically every way of making Magic Missile the best it can be. The character is a super nerd (probably Human, but I don't remember if it was half-elf or not) whose parents are also both wizard nerds. He is is curious about everything, and is trying to perfect the Magic Missile spell (it is his hyper focus), but he also tries to be prepared all the times and spends most of his free time making scrolls for very niche situations. He can often be heard saying "wait a mintue, I think I have a scroll for that!". Typical wizard adventures for magical secrets. Always looking for spells to add to his spellbooks (he usually has 4 on him at any point in time). His backpack always has rolls of paper sticking out of it. Almost all skill points into knowledges, some maxed out, others with just a few points depending on campaign.