I like exclusively Magnum for Bittering (generally FWH in my process), then Hallertauer, Hallertau Mittelfruh, Tettnanger, Spalt, Perle, and Saaz for flavor/late hop additions (typically at flameout, though occasionally at 10 minutes). The Hallertauer hops have been really low in alpha acids recently (I seem to recall a few years back when they were consistently around 4-4.5% alpha acid). Tettnanger seemed to head the other direction, oddly, as I had some 7%+ alpha last fall).
I have used Hallertauer as a lone hop, but it requires so much of it, that it can get pretty green in the wort. Likewise, I will bitter a Czech Pilsner with all Saaz every once in a while - but run into the same issue, so I prefer a bit of Magnum for bittering, instead.