What type of plastic can be used to produce your own filament? I'm considering purchasing Filabot or some similar filament maker.

What kind of plastic can I use to produce my own filament? Can I use any type of plastic or just specific printable filaments? Can I also mix different types of filament together or only one type at a time?
Filament manufacturers (for example, Colorfabb) also sell pellets, price per kilo would be about 10 times less than the same plastic in filament form.

Out of household garbage only ABS can be easily extruded into filament with Filabot-grade machine. PET AKA plastic bottles looks promising as well.

You can also use certain products "off-label". For example, string trimmer string (line) is simply a nylon filament and can be used as-is in modern diameter-agnostic hot end.