The first, and more easily apparent thing Bastiodon can do is threaten things.
Of course, that’s not apparent at all, but it’s a lot easier to figure out. You see, Bastiodon has access naturally to Metal Sound- and while the only Special Attack move it learns normally is Ancientpower, its pool of learnable TM moves includes all the staples (and some other interesting mentions) for building a Special Attack pokemon. This lets you get up to some shenanigans. Metal Sound will cut an opponent’s Special Defense by two grades- halving an unboosted Special Defense and effectively doubling Bastiodon’s power. Putting that together with a movepool that includes not only Thunderbolt and Ice Beam, but also Ancientpower, Flamethrower, Flash Cannon (for STAB), Thunder, Blizzard, Fire Blast and if you’re still in fourth generation Earth Power, you leave your opponent with a strange and unpleasant conundrum.
The first time your opponent encounters your Metal Sound, they will likely leave their pokemon in the fight and find a way to KO Bastiodon- either they spent the turn switching into an Earthquaker or something with Surf or Cross Chop, or they’re just not worried. Following Bastiodon up with a powerful Special sweeper or even a passable Special sweeper will punish them for this, forcing them to either switch and give you a turn, or lose whatever just clobbered the bulldozer. Worse yet, if they switch to something that can take out Bastiodon, you can still lay in a Metal Sound, thanks to Sturdy keeping the dinosaur up on its feet (if just barely) for a turn.
It’s after that that things become interesting. If they leave whatever you just Metal Sounded in combat after that, Bastiodon’s teammate will crush it or force a switch the moment Bastiodon goes down. Putting the right Berry on Bastiodon can also cause the one attack it might get to be terrifying.
If they start swapping when they see Bastiodon, then you’re ready with something to smash it good- either you’ve gone with standard Bolt/Beam, or you went to a nonstandard set just in case the resistances are different- I personally favor Flamethrower/FlashCannon/Ancientpower, since there’s very little that combination can’t at least hit neutral (I think Empoleon pretty much composes that entire list) and there’s always the chance to inflict a Special Defense drop or even better, boost everything Bastiodon’s got. With Sturdy on Bastiodon, you’re guaranteed at least one Metal Sound ‘boosted’ attack after that. And if they do that while Bastiodon is wearing Leftovers, then you stand a chance of Bastiodon recovering enough to maybe even do this again.
You can do something similar by breeding Screech onto it, but Bastiodon’s physical movepool is far more limited- 4th gen gives it Outrage and 5th gives it Double-Edge, and Stone Edge and Earthquake are always popular, but really, that’s all it’s got for good physical moves outside Heavy Slam. Giga Impact might be an option, but the thing is already slow enough, there’s no way it’s recovering from Giga Slam before passing out. If you’re going to use the defense-debilitating moveset, stick with Metal Sound, since at least that’s something that not much outside of Bastiodon can do very well compared to their usual functions.
The other thing Bastiodon is is a trickster.
It’s a very strange trickster, being slow and bulky and looking and acting more like a wall, but it’s hard to deny Swagger/Toxic is always a good start on Trickster activity, and the availability of troll moves like Magnet Rise (Earthquake this now!), Sandstorm (no more fear of water), Roar (Negative Priority? My speed is rated 30.), Stealth Rock, Magic Coat, and two of the other three weather moves (Rain Dance-Thunder, Sunny Day-Flamethrower) on something with Sturdy and silly-huge defenses creates some interesting potential.
Putting it simply, while you do still have to be careful with poor slow not-a-wall Bastiodon, putting it in the right situation will let this dinosaur really rule the earth- alongside its teammates.