They paid us today.
Not me (nem engem). They didn't give me my money.
We paid them today.
Not I (nem én). I didn't give anyone money.
Nowadays many (most?) English speakers would also use "not me" in the second example. But classically (19th century English?) the pronoun "I" would be used. (E.g., "It is I, the Count of Monte Cristo!")
In any case, the Hungarian does make the distinction.
Ah, you were curious about the different between én and engem, I guess? You're right, it depends on whether you're the subject (én - I) or the object (engem - me) of the regarding statement. It should become clearer when you translate your examples into Hungarian:
- Megölünk téged. Miért engem? - They are doing something to you, so your pronouns are in accusative case in both sentences.
- Te vagy a legrosszabb fickó* itt. Miért én? - You are doing (or in this case being) something, so your pronouns are in nominative.
(* maybe not the best word for "boy" here. I haven't got the hang of slang words yet.)
Another example where you're actually doing something:
- Arra a székre ülsz le. Miért én? - You sit down on that chair. Why me? (Why English insists on the accusative here is beyond me. Maybe cause "Why I?" sounds like you're starting to sing a song.)
That is applicable for any case endings you come across, two more examples:
- Hozzád dobom a labdát. Miért hozzám? - I'm throwing the ball to you. Why to me?
- Ezt a levelet neked adjuk. Miért nekem? - We're giving this letter to you. Why to me?
RyagonIV, you mentioned slang here, and that you are not claiming to be an expert, but I did not know there was a slang element to Hungarian. Should I come across it (if I recognize it that is) how is it considered in polite company? Is it viewed as discourteous, swearing, crude, sometimes acceptable, humorous, ignorant or downright insulting? When would it be safe to use it? Since learning real magyar vocabulary is sufficiently time and intellect consuming, I don't need to waste time on slang, however, it would be good to know how it is handled in comparison to English or Australian slang.
Still not an expert. :)
But I guess the rules for slang words are pretty universal among European languages. In formal situations you should avoid using slang words altogether. Then there are the harmless things like fickó or csávó, which are similar to the English terms "lad" or "dude". You should only use them among friends or family.
And there are ruder insults of which I have no examples, partly because I do not care about those a lot. :)
But I have heard (beware, second-hand information!) that swearing in general is a large part of daily interaction in Hungary. It might sound a bit rough-skinned but they don't mean it that harshly. I guess it's similar to American English and the copious amounts of "❤❤❤❤" going on in in the spoken language.