When I think of "smooth and sharp" my mind goes to, uh, I guess "sharp bilinear" is the most common term?

It's like nearest neighbor interpolation but with less artifacting when the zoom is not an integer. The middle of each source pixel becomes a solid color block, and then bilinear filtering is applied to the single-pixel-wide seams between each block.

It's equivalent to doing a nearest neighbor upscale to floor(scale), then finishing with bilinear.