Obby Maulers are fun, but can be a time commitment depending on how high you want your Strength.
I have one that was 99 strength (5 attack, 70 hp, 65 mage/range) at 50 combat. It's certainly fun to run around hitting 400+ at that low of a level. Plus, I've seen plenty of other Maulers that max at an even lower combat (46 or so), with lower hp.