3rd Gen Who became your most reliable HM slave?! (Besides Mew and other legendaries)

Azumarill. Though I did use him for battles and stuff, he was my highest-leveled Pokemon at that time. xD It was probably because, as a child, I felt that removing HM's were wrong lol

I used Tropius for Rock Smash, Fly, Strength, and Cut

Tropius and Wailmer can cover all HMs

Cut / Flash / Strength / Fly

Surf / Dive / Waterfall / RockSmash

I have three favorite HM Slaves on Emerald.
Tropius - Cut, Fly, Flash, Strength or Rock Smash
Linoone - Surf, Rock Smash, Dig (Dig was pretty neat too!)
Relicanth - Surf, Waterfall, Dive

It would either be Tropius + Relicant (Water) or Tropius + Linoone (Caves)

I use Marill for Surf,Waterfall,Dive,Rock Smash and Tropius for Cut,Flash,Strengh and Fly.

Makuhita's generally my go-to in Emerald for Rock Smash, Strength etc. Seaking was used for Waterfall, Dive, Surf then had a Beautifly with Flash and Nincada with Cut.

I think that would be Azumarril. Surf,Rock smash,dive and waterfall, I guess...can't remember if he can use waterfall...it's been so long since I had Azumarril xD.

Just to point out, I found it funny the way you assumed we use our legendary Pokemon as slaves to the cheapest moves in the game :P my Latios obviously knows Rock Smash, Strength, Flash, the like :PP, screw Psychic I want Strength.

I used mostly Linoone, Rhyhorn or Wailmer.

Even though I never wanted to, Swampert always ends up being my HM slave. I guess it's the curse of Hoenn and its water...

Tentacool can learn cut and all water hms. It's the best by my choice.