Objective or subjective pronoun?

Anonymous
Susan and me at Disneyland or
Susan and I at Disneyland

Actually, you can use either one.
The first is very informal; the second is formal.

The rule I've learned is that you remove the other person:

Susan and ??? at Disneyland -> ??? at Disneyland -> ME at Disneyland
You would probably not say "I at Disneyland"

So...
"Susan and me at Disneyland"

They're not complete sentences, so it doesn't matter.

I'd say "and me".

CJ

Since the pronoun is clearly not an object, I'd go with "Susan and I". It has stood the test of time for centuries, so I see no need to change now!

Hi Sam;

Suppose you come up to the front door of your friend's house. You ring the bell and your friend's voice from inside says, "Who's there?"
Which do you answer?

It's me.
It's I.

I would say, "It's Sam."

But, if forced to choose a pronoun, I would probably do what I usually do, and that is, initially, say, "It's me." and then hear my mother's voice in my head correcting me and say, "Well, to be grammatically correct, it is I."

She would always repeat the nursery rhyme to us, "It is I, said the sparrow, with my little bow and arrow."

If it helps, having read a gazillion autobiographies of famous writers, politicians, and other historical figures, when pictures from their albums are included in the book, and if there are inscribed legends on the pictures, they universally say, "X person and I at...." I've never seen a single one that said, "X person and me."

sam1947hear my mother's voice in my head

Ah, yes. The mother's voice theory of grammar. Not all mother's voices are the same, though. To "Who's there?" my mother might respond, "What's it to you?"

sam1947then hear my mother's voice in my head correcting me and say, "Well, to be grammatically correct, it is I."

I, too, was subjected to those mother-drills. But I realize now that language is dynamic, and acceptable forms change.

How often do actually you use "whom" these days?