You've met one, or maybe there's one in your group right now: The guy who plays the same character type over and over. Or worse yet, reincarnations of the same guy, or long lost twin with the exact same equipment, Kronk II, etc...
I believe this happens because of a love of the arch-type, or because of the ease of playing a character that you've played before. There's no searching through a hundred books if you exactly know which incantations you are going to take with your warlock, and have half of them committed to memory.
If I asked you to join my group with your go to character, what would it be? Which rules are you so familiar with that you could essentially draw up the character without fact checking? What would you pull out in a pinch?
For me, I've always had a stock wizard who self buffs(using the 3.0 durations of bull's str type spells) and uses utility type spells beyond that. I know that if I play in Fae'run I can gain some extra weapon or armor proficiencies to make this build work with the regional feats, and I have a few tricks up my sleeve with regards to making the durations longer, the metamagic easier, or the effect +6 instead of +4. Most DMs I've asked allow "Easy Metamagic" conditionally. The "Bite of" line of spells suits this guy really well.
Anyway, regardless of system, let me know in the comments down below what your go to character type is, and some of the tricks you commonly use to beef 'em up.