What about tickets to a concert or other event that he (and you--this is an anniversary gift) could enjoy together? My husband and I really had only gone to one concert in our 18 years together, but this last year we went to see Billy Joel and Jimmy Buffet. We had a blast, and really connected in a way we hadn't for a while.
Our anniversary was last week, and I splurged on tickets to see the Eagles in September. They're my huband's very favorite band, and chances are we won't get another chance to see them live. My husaband was thrilled!
Other than that, maybe planning a weekend away to some place relaxing that you could enjoy together. If money's an issue, maybe one of those not-too-far-away free timeshare resort weekends. You'd have to endure a one or two-hour spiel, but it could be worth it. (Just be SURE to say no--one excuse they can't combat is that you don't have time in your schedule to use it!)
Good luck, and happy anniversary!