(via zachelrath on github.com/skuidify) See Salesforce.com’s enhanced list component / Gmail for example of how this would work. Shift key intelligently selects / unselects items based on your most recent selection point, e.g. if there’s 3 rows selected, then a blank, then you select a row, and then shift-select a row 3 rows below it, the original 3 rows AND the new 3 rows are now selected, but NOT the row in between.
Building on Anna’s idea, the Shift key should select all rows between the first one selected and the row that is selected with the Shift key held. We should also be able to use the Command key (Mac) or Control key to select random rows (one at a time rather than bulk selecting all consecutive rows with the Shift key).