Oh boy. I've made over 200 sims, and 158 of them I've played with (rest were my own townies). It was hard to choose just one, but I managed to narrow it down to 4 (or 5 really).
Chance Matlock
https://i.imgur.com/HQnvmYD.png
He's a teenager who's a Serial Romantic and is well...Romantic. BUT! He's also a klepto. In the end I made him into a complete delinquent who fooled around with all the girls and stole stuff whenever he could (He cheated with all his gfs and stole from them after fooling around). Now I don't condone these kinds of acts in reality, but it was fun to play something vastly different to that of a normal life and what was more of a recipe for disaster, which is why he became one of my favorite sims. And oh yes - his parents died and the most famous detective in my sim world, Wolfgang, took him in and aims to correct his misbehavior no matter what!
Lys Dahlia (pronounced "lease" French word for Lily)
https://i.imgur.com/sDe0NHO.png
She's a Painter Extraordinaire, and is Creative, Outgoing, and is an Art Lover. She's not much different from a lot of sims I've made, but regardless, she ended up becoming one of my top favorites. She's very energetic and loves to socialize. Oh and she's a lesbian. She doesn't flirt much or anything, and is very respectful of everyone, but she's had a few crushes here and there.
Lumia Starlax
https://i.imgur.com/NxWvwQh.png
My first saved game actually got deleted somehow, and she was there back then compared to the other sims I've shown. I initially only made her as a live-in maid to a rich household. She was an alien back then, but in my current game she isn't (part of why I gave her such a last name). She was only ever good at one thing: Cooking, but she was a complete ditz about everything else, and that was one of the things that made me grow on her. It was just adorable seeing her try to better herself in other things; it really got me attached to her. She was also constantly bullied by one of her past household members (who was mean to everybody, but liked to pick on Lumia the most). This only made me want to care for her even more. She's also Childish, and it was adorable seeing her play dolls in the small room in the mansion she was given. Her childish trait is also the reason why she always dresses in a school uniform. Other traits: Neat, Foodie.
Lyonus Nightingale
https://i.imgur.com/O2FhHGO.png
I like him because he closely resembles how I dress, and he has had a somewhat adorable life, at least to me. He's a Creative and Gloomy Loner. What I like most about him is how he developed in his relationship. He fell for an equally creative gloomy emo-dressing girl named Paris. They met through their art club (same as Lys's), and shared a lot of interests. Eventually they started dating, and it was always at the museum during late night hours. Their relationship was the most adorable and I could write an entire essay on it, but mostly I thought it was because they both didn't like being with other people unless it was with each other, among plenty of things.
The fifth sim is the one on my profile pic, named Daemon Sentaric. In the past, he was a butler of a famous criminal family, but he left and used his skills to work towards his own mansion. He still always wears his butler suit though, because he feels like he was always made to be a butler. Though he worked for a criminal family, he wasn't necessary evil, although he lives in a red & black mansion. He's the type of guy who just "goes with it," as in he never gets angry, sad or anything. I basically built him to be a superhuman (all skills level 10), with custom traits: Awakened Mind, Determinator, and Neat. I always just wanted to have a perfect butler who could do anything.