Get him a bottle of Glenfarclas, and he will be well pleased. Superb stuff from a small distillery which is still family owned and run. Well worth a visit, too.
Don't think you're going to get an answer from this request, because everyone has their own individual taste. If I'm feeling flush and in need of a treat I'll go for Balvenie Double Wood. Tremendous depth to it from the sherry barrels it's matured in. Got a nice Aberfeldy from Tesco the other day for £25 down from about £40 if the offers still on.
Dunno if already mentioned, but what about a whisky tasting set where you buy a selection of different ones in small bottles?