For instance, Arid Mesa can be sacrificed to search your library for a Mountain or Plains card, put it onto the battlefield, then shuffle. While this can be used for basic lands of the stated types, it can also be used to fetch nonbasic lands with the given types
Although it comes with a relatively high base cost, Hunter's Mark can be used extremely cheaply against opponents playing Blue cards (ignoring their inevitable counter-spells, too), and to potentially devastating effect against Blue planeswalkers it's a tempting sideboard card
Cosmic Spider-Man I know Im supposed to mention Cosmic Spider-Man, but it just feels so forced, like Infinite Guideline Station from Edge of Eternities
The Jumpstart legend Bruvac the Grandiloquent looks to speed up that process, making this a good time to reevaluate the mill archetype now that a dedicated general exists