I'm not great with their scientific names just yet, but if you're okay with their common names then I believe the first one is a "string of pearls", second looks like a "zebra plant", third might be an echeveria "black knight", and the last one I've seen called "hobbit's trumpet/horn".

Senecio rowleyanus; Haworthia attenuata (not sure abut 3rd but I don't think it is Black knight?); last one looks like very etiolated Anacampseros....

The black one I don't think is 'Black Knight'. That plant pops up on the forum every once in awhile, and for the life of me I can't remember the name. I don't even think it's an Echeveria:). It's a nice plant whatever it is.

Oh wow... Lovely!

You guys might be right about it not being a "black knight" (it just looked like most of the ones I've seen), but I zoomed in and wow....I would really like to know what it is because it truly is beautiful.

Black knight has much longer, skinnier and overall bigger leaves. If you have seen some labeled as such, looking like OP's plant, they were mislabelled.

Ding ding ding you got it Chuckerfly:)! Never can remember the name. So I'm writing it down;).

Last one Crassula ovata "hobbit"? aka Trumpet jade or skinny fingers?

Helen

I don't think so...it has hairs, soft stems all over - unlike CO...see my comments (even if I am not absolute sure...)

@rina I've never seen that exact one labeled as a black knight at the store...it just looked like the true black knights I have seen until I really viewed the picture and zoomed in (the pic was a little small on my phone screen). Sorry about the original incorrect guess I'm still fairly new-ish to succulents and extremely new to this forum. :)

@ rina's Yes I wondered, seeing you didn't even have it as a Crassula. But one can only try :-)

Antlers - absolutely np...that's why you asked, right? Sometimes, differences are very slight and even growing conditions could make it difficult to ID even for ppl that may know. Just as your plant #4 - it doesn't look like Anacampseros should (check these very well grown Anacampseros plants -here- as grown by Kevin). But they have what I referred as 'soft' stalks (Crassula ovata has more woody and longer stems); and grow hair - CO doesn't - and that made me think it is Anacampseros. Few bottom leaves have shape similar to what it should be, rest are very etiolated. I do not believe they are tubular leaves as Helen is thinking...but the shape of leaves is confusing.

I wasn't the original poster of this question I was just a curious commenter, but I'm happy a learned a couple things from this thread even if the plants weren't mine. :)

And you aren't kidding about some plants being hard to ID....when I first discovered succulents all the info was almost overwhelming. I couldn't believe that two of the exact same plants could have so many small, unique differences and still be the same type. lol

My niece just visited Singapore, she send beautiful pics!!!

Last one is a Fenestraria Rhopalophylla i think.

I'd put my bet on Rina and Anacampseros.

I third the last one is an etiolated Anacampseros:).