Duuude!!! For everyone

"I'm terribly sorry I don't remember your name, it was..."

I ask there name, then I forget it 3 seconds later so I can be awkward properly.

If someone is with me Ill say to the unknown named person..”Oh, this is my friend Penelope.” And then hope the person says..”Nice to meet you Penelope, Im Fiona.”

Otherwise I say “I beleive we were both at the last xyz event but we were never properly introduced. Im Christie.”

"Dude", in my opinion, is equally applicable to everyone

I tell them I've forgotten their name.
It's up to them whether they tell me again what it is.

*** And I totally misread the original post. My apologies.

If I just met them, and it's not at all about having forgotten their name, I'd just straight-up ask them what their name is. I've never had an issue introducing myself to new people.

I avoid them.

"I know we've met, but I'm not sure I know your name. I'm Julie."

I just take a wild guess. Usually I start with Bob.

Dude.

Ma’am, Sir.

“Friend!” I actually get teased at work because I call everyone friend. I’m horrible with names.

If I had to get a strangers attention because they just dropped something on the way out of a store for example, I’d yell hey bro, brother, man, or dude for guys probably and scuse me, miss? for gals probably.

I don’t accept brother as being owned by Christians and black people aren’t going to think you’re being racist unless you are being racist and say it with a sideways tone. The last time this came up, it was a black guy that dropped his earbuds on his way out of a convenience store and I said hey brother you dropped your earbuds. I didn’t mean anything by it and would have called a white guy my brother in just just the same tone, and I think that was evident, hence not a problem. Whether you believe we came from Adam and Eve or evolution, we’re at most all 15th cousins and I refer to other guys as my brothers with that in mind. You could call everyone “cuz” to be less familiar/gender specific I suppose but I doubt if it’s often a big deal either way.

I tend to shout 'Hey!' at work until the right person turns around.

Human. It is my all-purpose go-to pronoun. Or at least I consider it a pronoun. Thought about using homo-sapien sapien, but thought too many people wouldn't listen past the use of homo.

hey man if female drop the man

The good old English standby - ‘mate’. Works with lady persons too.

I use 'human' for a gender neutral pronoun. I've had people be offended that I use human as a pronoun. No idea why. If I can't remember a name I simply ask how they spell it. If they look at me funny, I make up a fictitious cousin with the same name, different spelling. I was just curious because I always thought my cousin spelled it weird. My fictitious cousins would be so peeved if they found out.

Haha a third post from me -- sorry, it's late and i am not thinking clearly. if you know you don't know that person, instead of using a term, and if you don't just want to ask the person's name, introduce yourself! most people will respond to that with their own names. notable exception: harriet jones, intermittent character from doctor who, whose self-introduction (until her death) as an mp, then as the prime minister of the uk, then as the ex-pm, inevitably evoked (as a running joke) "yes, we know who you are."

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It occurs to me you may be looking for a word to use rather than a way to apologize or ask. but i don't think i have ever considered using a word such as the ones you've rejected (brother, sister) -- maybe that's just not how i think. i really would just ask for the name, unless i could get his/her attention without doing so (making eye contact, for example). i'd probably still ask. (of course if someone was about i could ask instead "hey, what's her name?" in which case that would be more discreet!)

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I generally say something like "i am rubbish with names. i'm sorry. i've forgotten yours." they don't have to know i never knew their names. i am uncertain enough in this situation that i don't know whether i've forgotten or never knew, but i don't think a detail like that matters so much. it's my way of apologizing for not knowing it, whether or not i once knew it, and at the same time asking for it (implied).

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I ask them their name. How hard is that?

I say Hiya my names Laura pleased to meet you the other will then most often respond in kind .

I ask their name.