My list:
Zilog Z80 - Still going strong; who hasn’t written code for it? Shit, my calculator uses a clone.
Motorola 6809 - Heart of my first love, the Tandy Color Computer. And a hell of a processor.
Intel 80286: It made writing 3GL code worth doing. Still a sucker for it.
Intel 80386: The same, only faster. Still remember a CAD demo using a 386 and being blown away. Made a few bucks around the Atlanta Olympics with one.
Subsequent models bore me because they aren’t so magically special.
You had 8 beautiful bits, 3 voluptuous registers, and how I used to love to pop your stack.
6502 - I will always love you.
+1. I loved programming 6502 in the C64 - using PAL. Wrote some great stuff for it.
Oh, the 6809. I thought of it as soon as I saw the title of the thread. The magic was gone by the 68040.
6502 for me too. I got a HesMon cartridge for my VIC20 and taught myself assembly language programming.
Ah, loves of my youth.
I have a great fondness for the Z80. My first micro was an 8080, and a wonderful learning experience. But programming Z80s was thrilling. The extra registers were just enough to be actually useful as a register-based CPU. 8080s choked on 16-bit operations and spent numerous cycles tranferring addresses in and out of memory. On the hardware end the design was better also. It provided automatic refresh addressing for dynamic RAM (64K of static RAM made a good space heater). An additional non-maskable interrupt was a life saver in adapting some of the wierd devices available at the time also.
I was also enamored with the sleek design of the 6502 and Motorola 6800. These guys were more memory oriented than register oriented. But they used simpler, faster, instruction cycles, and smaller instructions to run as fast as their fancier cousins from Intel and Zilog. And they were simpler more straightforward hardware designs also. You could make a computer with either of these processors using far fewer components.
However, just like help in the plumbing department at Home Depot, true love may only come once in a lifetime. Mine was the RCA 1802 COSMAC. This neat little processor had 16 registers, 16 bits each. Any of the registers could be configured as the program counter, and any of them could be configured as a memory pointer using an instruction called… guess what?..SEX. And it was sexy. That meant you could maintain 16 different stack pointers if you wanted to. And you could just switch program counters around instead of doing regular call stack operations. There were also special input and output pins on the processor that could be used for simple device controls, or emulating various types of I/O devices. The 8bit data path made it slow as all hell. But if you could imagine a fast version of this processor it would have made the others look silly. I had a chance to work for a company second-sourcing the COSMAC, and I regret turning that down.
There are plenty of others out there. Gaudily dressed 16 bit processors, and skinny 4bit slice processors. Even the 8bit family had a variety of exotic members. But you’re only young once, and you remember your first loves in a special way.
Had to quote, just for the name combination. 
I learned assembly on the 6502. Spent some time architecting things on a PIC for one of my phones. But I’m kind of partial to slightly larger things…I learned how to make cell phones on OMAPs. Those are the first chips I ever did board bringup and OS porting for. I miss those days.
-D/a
Listen Digital, you can quote Analog but despite your name, you’ll never be Analog because you’re far too discrete.
IBM 360.
What ???
It’s less powerful than many current microprocessors.
BALR 14,CoolAddr
SVC 3 'forever baby
Everyone’s doing it though! It’s the new thing!
Ironically, I’m actually doing some analog stuff at work these days…power and audio. If this keeps up, I’ll have to change my name.
-D/a
I loved this proc but didn’t know it until I saw what my friends had to deal with on the 6502 - more limited addressing, fewer or no 16 bit operations, no MUL.
Learned on the Z80. Excelled on the 6502. But fell in love with the ARM.
Also, no way to push or pull the X and Y registers — until the 65c02 anyway. Pity the 6809 wasn’t in more machines.
The Motorola 68K family is my old favorite, and still lives on as Freescale’s “Coldfire” and “Dragonball”.
MOS 8502, a 2 mhz version of the 6502. Used only in the Commodore 128, AFAIK.
And, related, my favorite coprocessor: MOS SID 6581. Preferably two of them, for stereo. 
I’m intimately involved in the design and manufacture of one processor family, and was involved for a short time in the original version of another. For ones I used, I wrote a simulator for the 8086 in grad school when it first came out, and I had a development system for the Bell-Mac 8 which I used to debug tests I wrote for it on another simulator.
My first disappointment: TMS9900 in the TI 99/4a
First love: 68000 in the Amiga 500
In between, the apple ][ writing stuff like a mouse handler and ‘sprites’ (in quotes, cuz they weren’t, really.
But man that great big 3D animated ball, with shadow? Love.
Trying to remember the mini that had a blowup instruction. OK - BLWP (Branch and Load Workspace Pointer), but pronounced blowup. I like any computer you can tell to blowup!
My first meeting of the Color Computer club someone had retrofitted a TRS-80 Model III case with a CoCo3 motherboard and an RGB monitor and was running a clone of that. Not as hires, but totally cool: Boink Bouncing Ball demo on CoCo 3 - YouTube
Oh, wow, that takes me back. My introduction to low-level programming was this book: Mastering Machine Code on your ZX81.
Goddamnit, I thought this was going to be about silicon-based transistors, like the newish Intel 3D. WTF do I care about some processors??!!!
My vote’s for the 3D Intel – cool design, but it’s not a processor, so my vote doesn’t count.