No. 4: Dad needs a gadget
Whether your dad is really into technology, or just dabbles, there's something out there that he can really use.
Technology moves so quickly now that you can use Father's Day as a great time to help Dad update what he currently has. Do some research and see where he needs an upgrade. If he's really picky about his purchases, you may need to be sneaky and ask him questions yourself.
If it's in your budget, help Dad update his cellphone. Get something that you know he will love and that he'll use. Consider how he'll use a new phone before buying one with all of the bells and whistles.
Help him catalog his old CDs with a new MP3 player. Buy him that digital camera he's had his eye on, or a Kindle or Nook. You can also buy great accessories for the technology that he already uses.