If you want a fish that will fight and make a nice mount, I would get a guide and go after tarpon. There will be 100+ pounders around in May. The same areas that hold tarpon will also hold sharks and barracuda. The barracuda will be smaller than the tarpon but fight well and would look cool on the wall. Any decent guide could find you a nice 'cuda. Many fishermen will be trying to avoid them as they cut their leaders and bite their fish in half. If you troll offshore, you will have your chance at the biggest fish and the toughest fighters. However, the big marlin aren't exactly common and you might get skunked. You'll catch plenty of mahi and a 50 inch mahi would make a pretty mount. They also fight well and jump often. Sailfish are good fighters and make great mounts but they will be getting pretty scarce by May. They're more common in the Keys from November through March. Wahoo and tuna are always a possibility but not something you would target specifically (with the exception of blackfin tuna but they are small as far as tunas go and mostly for eating). One other possibilty is to tell the guide you'd like to catch photograph and release a goliath grouper. These babies can be several hundred pounds and a lot of guides know where to find one. They're protected so they're always released. Sounds to me like you're a candidate for either tarpon fishing or offshore trolling. Call a couple of guides and tell them what you want. They can put you on something that will fit the bill. The swordfish is a real long shot, though. That's a deep water, night fishing gig and I don't know if any day time charters would target them.