i have OB, skyrim, FO3 and FO:NV which have sidekicks. i am not sure if other games here have sidekicks.

i like clover from from FO3. she can wear cut outfits, she flirts, and has some interesting lines when she gets into fighting.

Have you ever played Morrowind? There were rare occasions where you would have a follower. The AI was not the best back then. If you changed elevation slightly, the follower would assume you had climbed a mountain, and would proceed to run in the opposite direction, trying to run the long way around to find you. Having a follower in Morrowind meant having an idiot who you spent ages chasing up and down foyadas.

I think Serana in Skyrim had the most interesting set of dialogue and interaction with the world. Recently though I'd got quite attached to Eola, the one-eyed cannibal nightblade. Mostly because she actually uses the offensive spells she has, instead of casting a shield spell and then trying to fight with a dagger.