I know people are often scared of tweaking the fuses because you can "ruin" the chip by disabling the reset or changing the clock to require a crystal. I found an easy circuit for making a high voltage programmer that will let you set the fuse no matter what you did to the chip.
This way, I can easily use 6 pins for IO and then change the chip back to having a reset pin for programming again. You just need a source of 12 volts.
I made a little stand-alone attiny zapper from an Arduino Nano clone that doesn't need a computer connection. I have 3 push buttons wired to change the fuses to whatever I need.
- 8 Mhz internal clock
- 16 Mhz crystal clock
- 8 Mhz internal with no reset pin (to get all 6 I/O pins)
2 LEDs to indicate it worked (green) or failed (red).
If there's any interest, I can throw the code up on Git Hub. I modified the code slightly in the instructables example to handle the buttons and LEDs.