Was he involved in Air Fortress at all? I just picked up this little NES gem recently, and noticed it had the Hal name on it.
As far as I've read, I believe that he directed it. That game is great, kind of a cross between a simple shmup and a better version of Baraduke but without I'M YOUR FRIEND. I've heard that in North America, it only got released as a Home Shopping Network/QVC mail order-type deal, and it would look a little dated upon a 1988 release, but the gameplay sure shines through.
Was he involved with the Adventures of Lolo games? I adore those and I don't see them being mentioned. Anyway, Kirby and SSB are two of my favorite series ever, Pokémon Silver is my favorite Pokémon game and I need to play Earthbound since I got it for free on Club Nintendo somewhat recently.
Rightly or wrongly, I somehow always kind of associated him with the Lolo games growing up. I saw something that said that he at minimum made the stage editor for the first Famicom release of the series, but it sounds like HAL was so small during the '80s and early '90s that pretty much everyone there probably had some sort of hand in every game. I don't see his name among the title screen credits of the original MSX Eggerland Lolo games, though.
It seems like between Rollerball and doing NES Pinball for Nintendo and the golf games that he was pretty well involved with at least the codebase for HAL's ongoing pinball (Rollerball, Revenge of the Gator, Kirby's Pinball Land, Pokemon Pinball GBC) and golf releases (Hole in One for MSX and SNES, the FDS Golf games, NES Open Tournament Golf).
Everyone interested in Iwata's programming background should probably watch
his Balloon Fight mini-episode of Game Center CX.