Perform the following actions to unlock cheats which you can toggle on in the Options menu. Note: You can only use cheats while replaying memories.
Beat Sequence 1 with 100% Synch - Ride the Unicorn / Turn all horses into Unicorns, weapons are electric
Beat Sequence 2 with 100% Synch - Buns of Steal / Invincibility
Beat Sequence 3 with 100% Synch - Killing Spree / Assassinations cannot be blocked
Beat Sequence 4 with 100% Synch - Sisterhood / Assassin's Guild recruits are all female
Beat Sequence 5 with 100% Synch - Ultimate Guild / Assassin's Guild recruits are Assassino rank
Beat Sequence 6 with 100% Synch - Calling all Assassins / No cooldown timer when calling Assassins
Beat Sequence 8 with 100% Synch - Desmond Everywhere / Desmond skin