Most of the creatures you can train are only decorative. However, the legendary pets have many useful features, such as sending items to the bank (now and then), picking up monster drops automatically, doing high alchemy without using runes (now and then), and others.You can buy a legendary pet with a few bonds. You may also get it occasionally with certain promotions.
Update: If you mean fighting against monsters, that really depends on your levels. One thing you can do is slayer tasks; that way you get a variety of monsters, and you train all your combat skills, including slayer. Slayer monsters give great drops, too, especially at higher levels. In general it's convenient to use the highest-level slayer master you have access to.
a nobermom
Hill giants.
Green dragons
The best monster to kill in Runescape would be the King Black Dragon.
Scorpians.
i believe that experiments are the best to train on because they have 100 hp and hardly ever hit you. when they do hit you they only hit 1's they can be found near fenkenstrains mansion
Kill Fire Giants at Baxtorian Falls ( Members ) You can train yourself anywhere as long as there is a monster to kill.
There is a "Demon" at the top of the "Mages Tower"in "Draynor Village" that's excellent for Ranged and Magic training alike.
mokey if you want to train prayer
The best spot on Runescape Train Attack is in between lumby and vorok, go to beefy bill, or in al kirid fight guards with friends.
A good way to train combat in Runescape is to go to Soul wars. whats the best thing if im nonmembers
You can train on hill giants or moss giants.