Things to do in assassins creed?

Assasins Creed: Collect the Flags in each City/Zone.

Kill the Templars.

Assasins Creed 2: Improve the Villa

Collect the Fethers

Purchase all Armor, Paintings, and Upgrades.

Complete the Codex Collection

You can also kill guards, and civilians, but not horses. Oh and you can also kill yourself :)