Basic Components of Embedd

There are some basic components to be know by each and every developer or hobbiest . I will let you know some basic components that i feel that are basic to learn.
List:
--> Led
--> SSD (seven segment display)
--> LCD Module
--> Switch
--> Matrix keypad
--> serial DB-9 how is it connected.
--> External Crystal
--> Resisters & Capacitors
--> Potentiometer
--> Relay
--> Regulator
--> Pull Up and Pull Down
--> RTC (Real time clock)
--> SMD Resisters
--> Watch Dog timers
-->MCP2122 (IR encoder & decoder chip)