I'm a fan of what I call the semi-preemptive 3NT based on a good minor suit (or minor suit fit). It makes it awkward for the opponents and has relatively little danger for the bidder. If they double, we can usually go back to 4m.
Incidentally, I recently heard a funny story from Andrew Robson on the Sorry Partner podcast. In the story, at favorable vulnerability, he overcalls a 1C opening bid on his right with 3NT, having eight solid diamonds and five tram tickets. LHO, a world class player, doubles and leads a heart. [Andrew had no good explanation for why he didn't "run"]. Dummy comes down with eleven worthless cards, a diamond and... the ace of hearts!
But here's the hand that happened to me just last week:
When I bid 3NT in this auction, my robot partner did not understand it as a semi-preemptive 3NT. He bid 4NT (invitational to 6NT). Naturally, I had no aspirations for slam so I just passed. As you can see, this was the first board of a tournament, and I was tempted to just give up. But I played on, going quietly off two.
The result was a 100% board! The opponents had slam available in hearts (although nobody bid it). A few people were in 5DX for -500 (a bottom). The rest were all in 4H making six. Best defense would get me down three but, undoubled, that would still be a top board.
I wonder what would have happened if partner had not bid 4NT. Maybe the robots would have re-opened the auction and things would not have worked so well for me. But that's the beauty of preemptive bids--especially those that look like they might be to play. And, as we saw above with Andrew Robson's story, every now and then, you actually get to make your crazy contract!
