I liked programming the m68k cpus. They were also the CPU used in my computer science department curricula for assembly language programming classes.

At school we had lots of Sun{2,3,4}, Apollo, HP, Mac, and NeXT computers which we could practice on. Kinda saw the writing on the wall when we got a 6 CPU i386 sequent symmetry system and then SPARC, MIPS RISC, and PowerPC while nothing really from Motorola. I never enjoyed programming x86 cpus after being self taught on 6502 and then m68k systems :-)

I still have an ATARI Mega ST and a Sun 2 at home for sentimental reasons only.