This year, I lucked out and came up with a couple great ideas. I'm getting my dad a butterfly house kit (the wooden kind they roost in overwinter), and to go along with it, my daughters are getting him a personalized hammer that says "Papa, we love building memories with you" on the handle. Other years, I've had some major difficulty, cause he will never give me ideas. But he absolutely loves nature, especially butterflies and dragonflies. For his birthday in March we got him a gift certificate to a place that you can order butterfly larvae (caterpillars) from.. he's been finding Monarch caterpillars in years past and bringing them inside to complete their life cycle, then releasing the butterflies... so figured this year, he could try a different type of butterfly (that's legal to release here of course).