My biggest gripping fear is having to travel with a bunch of colleagues who are total amateurs.
Y'know, the guy who checks a bag on a 2-day business trip. Or the guy who insists on working with the airline to get your seat assignments next to each other. Or the guy who wants to overschedule every single moment of nonworking time and is then 15 minutes late to every planned meetup in the hotel lobby. Or the guy who's never been to New York before who wants you to go to dinner in Times Square, even though you purposely stay out of that part of town on your other 100 trips to Manhattan.
Any version of that guy. That's my gripping fear.