Ser Jacopo, Ferndown, Johs, Jerry Perry, Savenelli, Chocum, Butz-Choquin, Peterson, Missouri Meerschaum, Old Dominion, Bari, Nording, Dr. Grabow, Benton, among others.
I'm new to pipes. My current favorites are Peterson (I've started with this brand and own a B5 Bent Bulldog and a 106 Billiard), Dunhill (beautiful pipes), Castello, and Radice. Of the two Italian brands, I like their Pots and Billiards. I'm also attracted to the Dublin, Bent Dublin, and Poker shapes. The Bent Apples also look good. I'm a Sherlock Holmes fan, so I may have to get a Peterson or two from their Holmes collection.
Peterson remains my single favorite. All the other companies represent occassional pipes. And I've learned by expensive experience to stick to the billiards, either bent or straight. Second in number of pipes would be Nording, of which I own about 5. I have a black dress Nording Dublin with a large chamber that never fails to provide a good smoke.