In order of preference
Champagne Krug, Reims
In my view, the best there is, from the “regular“ Grande Cuvée to the vintage to the Clos du Mesnil. The Rosé is a bit more expensive than it should be, and the Clos d’Ambonnay is much more expensive than it should be, yet this is hands down the very top.
Champagne Jacques Selosse, Avize
Probably the most skillful and innovative récoltant-manipulant working today; not inexpensive but worth it, especially if someone else is paying.
Champagne Salon, Le Mesnil sur Oger
Salon is a top classic collectible, steely and very fine, but takes a long time to come around.
Champagne Bollinger, Aÿ
One of the greats; Vieilles Vignes Françaises is the top cuvée, yet the RD is also superb and the Grande Année vintage is a solid value.
Dom Pérignon, Épernay
The inimitable classic and one of the best champagnes for aging, full stop.