So there's a spiritual successor to the game Total Annihilation called Planetary Annihilation*.
It's currently in the "playable beta" stage, and features heavily TA-inspired gameplay (and music, and basically everything), but has a critical difference: Instead of being played on bitty square maps, it's played in bitty solar systems, with actual spherical planets.
And as one can see in this trailer, space travel and planet busting are things; in fact, one can build giant, vaguely Kirby-esque engines** and use them to drive planets into other planets.
While this doesn't strike me as the most efficient way to go about wrecking planets, it does strike me as being one of the more awesome ways to do it.
*This is confusing for someone who was in the Total Annihilation community at its height like I was. There were three big sites back in the day: TAUniverse (the big, well-policed fansite that hosted many smaller sites and was generally the best site period, which is the only one that's really still around), Estrella (the shady, dodgy site, where I'm pretty sure you could pick up some stolen content, such as an illegal copy of the game), and PlanetAnnihilation (a site modeled after TAUniverse that was part of a larger, corporate webhub called GamePlanet or something, which despite its corporate sponsors always actually felt like it was more questionable content-wise and significantly less friendly and usable). It might get better, seeing as how I've only heard of Planetary Annihilation days ago, but I'm still blinking in confusion whenever I read it.
**I'm probably looking at them and thinking they're Kirby-esque because they're square. They really aren't that Kirby-esque, but they inexorably remind me of the engine that Galactus put on Ego the Living Planet in the '90s-era Fantastic Four cartoon, which was almost certainly Kirby-derived artwork.