My advice -- do something memorable and different. Cufflinks, flasks and business card holders have been done and people tend to forget about them. Also, if you're like me, they become awkwardly obsolete when you get divorced in 5-7 years.
Go camping in the mountains and grill out, rent a place at the beach for a weekend and go surfing and play wiffleball on the beach.
The best gift is a story you can all share in for years to come