TickTick
TickTick brings task lists, calendar planning, habits and focused-work timers into a cross-platform personal productivity app. It also supports shared lists for lightweight coordination.
Blitzit
Blitzit is a personal task manager and focus timer built around executing the next task rather than administering a large team project.
NotePlan
NotePlan combines notes, tasks and a calendar in one planning workspace, with native Mac, iPhone and iPad apps plus web access.
Routine
Routine combines tasks, calendars, notes and custom databases in a connected workspace for individuals and teams.
Things 3
Things 3 is a personal task manager built specifically for Apple devices. It organizes everyday responsibilities and larger projects without trying to become a shared team-management system.