One gift I think is great for dads is a round of golf at a nice course. Of course, you say he has no real hobbies, so I assume he probably doesn't play.
Tickets to sports events and concerts area always good, like Lionlove mentioned. Also, you could do a gift certificate for a nice restaurant -- that's my parents favorite, I usually get them $100 or $150 to a really nice steakhouse.
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