For me it was Z80 Assembler on the Z80, then 6502 and 65C02 Assembler on the BBC A, B, 2nd processor. To be very honest, I used to hack various Beeb games to make them work using a disc drive for faster loading. Later on I re-wrote part of the OS to make it much faster using the 65C02 and enhanced instruction set, whilst also using the "un-authorized" or "undocumented" instruction set on both 6502 and 65C02 to make stuff run faster.
Split screen programming was my thing with I think Modes 1 and 3 intermixed from memory; would need to dig out my documentation for that to verify. I also wrote a complete Bulletin Board System for Radio Hams on 2m using the cassette port to produce the right tones for coding over the air together with Morse code transmission from the beeb, again using the cassette port, which was a requirement for a server/repeater ident.
Pascal, Forth, Fortran, C, C++, C#, ipx86, Java are languages to name a very small amount of my repertoire, then of course there is XHTML, XML, XSLT, CSS, and now of course HTML5, but I don't do these any more. Python, Lua, Javascript, VBScript I have also have plenty of experience with.
Currently, when not playing Elite, (which exploration is taking a huge chunk of my time), I am writing a DXD Engine using C, interfacing with Lua for the scripting side. This will then be used for examining a new method of AI written in C++, which is a self evolving new type of neural network, (hush hush of course). It is all my own work and ideas and one day, I may publish something about it for others to take up mission.
I am essentially self taught with all languages, just referring to manuals when I get stuck on sort of syntax or knowledge about some obscure object. Programming has always been a male orientated subject, and when I first started out, I couldn't get any kind of job with computers, so I had to work my way in through the back door. It is still hard to get a job even these days, and even more so when you are disabled.
Sadly these days, I take quite a few strong painkillers, that turns my brain to mush, so my programming is very limited at the moment.
The older you get, the more experience you gain, so if it looks as if I have done a lot of stuff, it is because I am a dinosaur.
My favourite will always be 6500 family assembler. I used to dream code in those days.
K