I had the benefit of growing up with a geeky dad (and mom, too), though he probably wouldn't refer to himself as that. He's always loved computers, space travel, nature specials, Dr. Who, and other fantastically geeky stuff, and he passed his fascinations onto me. If there's a geeky dad in your life, why not make him the ultimate geeky toolbox this Father's Day?
Wired magazine's GeekDad put together a helpful and concise - but surprising - GeekDad Toolbox Must-Have Hardware. Some of my favorite suggestions are bulk garage sale LEGOS, a cordless rotary tool and membership to a community-run maker shop. (I know there are a couple of these spaces in San Francisco, and I have friends who are huge fans. Are there any in your area you recommend?)
In addition to Geekdad's recommendations, I would add any or all of The Geek Dad Books, a subscription to MAKE magazine, a roll of gold duct tape, some stainless steel zip ties, and DVDs of his favorite iteration of Dr. Who.