Krabby/Kingler is a good one.
It learns cut, strength, rock smash, and surf.
But why would anyone use such a good pokemon as HM slave? Other choices are better.In LG catch both Snorlaxs have one as a HM slave it can know Surf,Strength, Cut(I think) and I think Rock Smash.
Check serebii.net to see who can learn them and stuff.
Yes, you need to be patient.... I know you said you have seen him, but just to confirm, you only see Entei if your starter was Bulbasaur. Anyway, good luck ^^
Actually, I've found it a couple of times already, using the Route 2 method... but now I've caught a Wobbuffet and I've actually come prepared, I can't get him to show up! I'm not being impatient, I've just gone through about 50 Max Repels so it's fair to say I've given it a good shot!
In Ruby, is Manetric/Electrike any good? I caught a Electrike and a MINUN and the Minun is miles better, but only a couple of levels higher. Is it worth trainign Electrike or just bolstering Minun?