Useful Pokemon are to say is Typhlosion ,Ditto,Red or Blue Gyarados,Dartini,Togepi,Onix,Geodude,Meganium,Porygon and Fearow .

Now,for the suitable Pokemon for suitable out using powers.Typhlosion is suitable to learn Cut which helps to cut down the Trees.Meganium's Poison powder and Razor leaf are the Powerful Leaf type powers.Onix,Geodude and Machop or Machoke are suitable to learn Rock Smash which can used to smash rocks and Strength which can be used to move Boulders, Plus these Pokemon are Prowess in Rock Type.Porygon can steal and Change it's own type other any other types too,For an example; it can turn from Steel to Rock type.Both red and blue Gyarados,Goldeen or Seaking and Dartini are suitable to learn Surf, Plus these Pokemon are Prowess in Water Type.Spearow or Fearow can be prowess on Air and they are suitable to learn Fly which can be used to fly from one destination to another.Ditto and Porygon can be mostly useful too because Porygon can change it's type and Ditto can transform itself to another Pokemon.Togepi might be alike Baby but it also like Pikachu which can learn Moves and it won't betray it's leader and it also suitable to learn Flash which can be used to illuminate Dark areas like Caves.These Pokemon are useful in Silver or Gold,but I prefer that they are mostly useful in Silver.