Taskade is a beautiful project management tool for both personal use and team collaborations. Taskade ships with task management and …
Anydo comes with a very useful daily review and reminder. Anydo also integrates with its own utilities such as calenders.
Not so lightweight but still very good for managing life especially since it has got a lot of integrations from a lot of other services.
Google Keep is light-weight. It comes with powerful search. The App ships with simple drawing and handwriting.