A fillet knife is always a good gift for Father's Day (June 21). But research is required to purchase a knife that gets used, not left in a garage when Dad heads to his favorite lake in search of dinner. Budget, in part, will determine whether Dad gets an electric (expect to spend $50-$100 for a good one; cordless electrics are most useful) or traditional-style knife. Many of the latter are inexpensive. But for a good one, you might pay as much as you would for an electric. Most important in a traditional-style fillet knife: Buy one with a flexible blade, so it can easily remove both bones and skin from a fish.