I don't mind a tough par-4 as an opening hole, such as the one at Crystal Downs. I approach it with the expectation of making 5, and the goal of keeping a 6 off the card at the start. If I make 4, awesome, but it doesn't happen very often.
Several of my early courses started with par-5 openers -- Black Forest, Stonewall (Old), Apache Stronghold, Barnbougle, and St. Andrews Beach all start that way. I've decided I don't really like that opening gambit, because it's too easy to screw them up and have a 6 on the card right away. But, I'll still build a par-5 opener if that's what the land [and the other holes] tell me I should do.
My favorite of the opening holes we have built is probably Old Macdonald. There is all the room in the world to hit it off the tee, and a huge green to hit if that's all you want to try for, but going at the flag is a lot more testing and could put a big number in play. Lost Dunes and Tara Iti also have opening holes I like, and in fact they are a little bit similar.