Which arduino should i use for a very simple one pin "blinking led" type project?
For beginners, use an Arduino Uno. It is ready to use and quite expendable with shields. They have the USB to SERIAL chip on the board. Only week point is that it is sometimes large from space sensitive projects.



For more advanced users, I would suggest the Pro Mini (my personnal favorite). It is small, powerful and even has more pins then the UNO. The main disadvantage is that it requires an FTDI connector for the USB to SERIAL. Note that this NOT recommended if you use a lot of I2C.



Finaly, there is the overkill option. Only use this if you are considering to get one Arduino to rule them all!. It's the Arduino Mega 2560. It is the overkill of the overkill. So many GPIOs and ANALOG inputs. It is also unique for its core which is different the then normal ATmega328.



Then finaly there is the most easy to use one, the Red Board by Sparkfun. It combines the best of each Arduino in one. Note that this one is not manifactured and backed by Arduino.



That is pretty much a summary of all of the most popular types of Arduino that there is.

[EDIT]

Note that none of them has an included case and a circuit that can reduce 220V to 5V. If you really want a case, get an UNO. There are many cases for it. For transforming 220V to 5V, use an 5V wallplug. If you have something like a 12V wallplug, you can also connect it to the Arduino but you have to make sure you connect it to the Vin port.