I'm still a beginner, but now that I've tried enough tobacco blends to say that my top and bottom five don't overlap (and that there are even a few blends to buffer the middle) I might as well make this post.
1. Burley London Blend (Mac Baren, sun-cured Burley/Virgina) - This is the first blend I can imagine smoking all day long, if only I could. I especially like it in my cobs.
2. Orient 996 Vintage 2007 (McClelland, air-cured bright Virginia/red Virginia/Yenidje/Latakia) - Despite the weird tomato soup smell, this stuff smokes beautifully. It's my favorite nighttime smoke to relax by.
3. Hazelnut (Lane, air-cured golden Virginia/Burley, toasted Cavendish) - This is far and away my favorite aromatic, and a guarantee that I will never turn up my nose at aromatics, Cavendish, or bulk blends in general.
4. Carter Hall (John Middleton, air-cured Burley/Virginia) - I have CarterHallJunkie to thank for turning me onto this blend. It's the best bang for the buck, in my opinion, and I like it better than a whole bunch of tobacco I paid a lot more for. I also have to acknowledge tiltjlp for his continuing espousal of OTC brands.
Fifth place is a toss-up.
5a. Black Cavendish (Lane, fire-cured black Cavendish) - When I first took up pipes at the beginning of the year, a lot of (hopefully) well-meaning storekeepers directed me to a variety of sweet, bulk aromatics. This is the first one that stuck, and for a while it was my favorite tobacco.
5b. Black Cordial (Lane, fire-cured black Cavendish/Virginia) - The copy promises something "dramatically new and different in taste and appearance." Yeah, right. That's a miss on both counts. Despite the puffery, it's still really good. The overall experience is very similar to Black Cavendish and vies with that blend for my favor. It also has the distinction of being the one pipe tobacco that always seems to attract positive comments from passersby when I light it up.