yeah, there were quite a few non-evolving pokekmon in gen 3, now that I think about it.
torkoal, kecleon, skarmory, tropius, sableye, mawhile, minun, plusle, volbeat, illumise, roselia (at the time), spinda, zangoose, seviper, chimecho, lunatone, solrok, castform, absol, relicanth, luvdisc, nosepass (at the time)
and a lot of pokemon that evolved only once.