Norwegian has special cabins for singles on their newer ships (Epic, Breakaway) Cruising is a very stress free vacation with one rule: Be on the ship before it leaves.
Wife and I have been on 8 and had a great time every time. We've also traveled traditional air/hotel style to Europe, Caribbean and various places in the US and found it works just as well, it's vacation.
The best trip ideas depend entirely on what you wish to do. Personally, I dislike hanging around a hotel pool, even if its really nice so resort only places like Club Med, Sandals don't do it for me.
If you are just looking for a beach to sit on away from civilization there are plenty of those. If you are looking for off site activities, it's hard to beat Hawaii. But I also like the BVI, St Martin, Antigua, and USVI (specifically St John)
I like to ski, so Jackson Hole, Vail, A-Basin in the US and Italy, Switzerland and France in Europe.
If you are looking for a party Key West is hard to beat.