bright LED on IO-Pin without additional transistor (PIC 12F)
The issue with using a microcontroller's GPIO pin directly, to operate an LED brightly, is that the current that passes through the LED to light it up, also has to pass through the GPIO pin and out through the microcontroller's ground pin, for the circuit to be completed. This is called sinking of current. 

While many microcontrollers are rated for sinking 20 mA or more through an individual GPIO pin, some are not. More of concern, when one has multiple such current sinking connections, these currents add up at the MCU's ground pin - which itself has a limit, differs from MCU to MCU. 

Solution: Drive your LED with very low current if you absolutely must save on the transistor. A typical indicator LED will light up pretty brightly even with 3 or 5 mA of current - try it for yourself.