Rock elementals are extremely tough to kill or knockout. Over encumbering them inside or around your base and setting them to aggressive allows them to defend your base with their rock throw attack without being kited away by enemies.
If our tribe goes egg-stealing, we always have at least two tribe members on Golems at the edge of World's Scar. When he stealer flies away, the Golems agro the wyverns and kill them all (immune to elemental attacks) for TONS of free milk
Pretty much the giga of scorched earth. Can damage stone, which is nice in pvp. It can throw rocks. This does massive damage to creatures, but does none to structures. Be aware of homing rockets though. If your opponent uses homing rockets, then it doesn't take too much to kill it. If you're not using it actively, you can also disguise it as a rock and put it somewhere around your base. This is a death trap for any raiders coming to attack you!
By adding ramps on a paracer platform saddle, you can exploit a glitch that makes the elemental's weight not affect the paracer. You can use this to gather massive amounts of materials. (Have one person drive the paracer, while someone else rides the elemental and harvests)
All non blunt force/ explosive damage is reduced to half. To add to that, with a primitive saddle, all damage is reduced so it takes about 30% damage. Always have it disguised as a rock around your base. It works better than a vault in several different situations. (For ALL smaller bases)
Have a good weight Argentavis (with a saddle, so you can craft behemoth gates) filled with thatch following your golem (on high range works the best) and get wood & stone with the elemental. Transfer the wood & stone you get into the Argentavis and make Behemoth gates. You can also just make other stone stuff, no need for argent but remember to bring thatch!
If you place a platform saddle on a parcer and make it have sloped ceilings going down to the ground on the side(s) you can then put rock golems on the ramps you can get infinite rocks/metal without having to worry about the weight limit on the parcer or the golem
The rock elemental is an amazing gatherer mostly for stone, but also gets some insane amounts of meat, and keeps it from getting spoiled for a good amount of time. Rock elementals also are one of the best defenses against dragons. The rock throw attack seeks the nearest target agains you to make the attack a little easier to make contact with target