Always joked about it being doable. Hypothetically speaking, if attempting a nice, easy Pokémon game like X/Y using a team of 6 Unown, what type of Hidden Power attacks would you opt for? You'll probably want at least 1 Psychic for STAB.
I recommend any of these:
1. Hidden Power Psychic for STAB
2. Hidden Power Fighting for Dark, Steel, Rock, and Ice Types
3. Hidden Power Ghost for Ghost and Psychic types
4. Hidden Power Ice for Dragons
5. Hidden Power Poison for fairies
6. Hidden Power Fire, Flying or Rock for Bug Types