For the Grill Master Dad / Gadget Lovin' Dad, a Grillbot the automatic grill cleaning robot - Rumba has got nothing on this guy.
For the Dapper Dad, a FATHER Blue Stripe Handkerchief from Forage Haberdashery. Truthfully, anything from Forage would make a great gift for a dapper dad.
For the DIY Dad, a Ryobi 18-Volt One+ Lithium-Ion Super Combo Kit from the Home Depot, the trick with power tools is to buy something you think he'll like, but always give him the receipt - he can return them and use the credit towards the tools he really wants but you can't afford to buy him (it works out well for you both, you get credit for the big better tool and he can justify his purchase to your mom)
For the Every Dad, a Duct Tape Coffee Mug from Perpetual Kid, no explanation needed.