Magnum is a great bittering hop with an aroma similar to a strong Willamette. It therefore works well with Willamette, Fuggles, and British Kent Goldings when used as an aroma hop in later boil additions.  Magnum makes an incredibly useful bittering agent in just about any beer, and due to its very smooth bitterness, you can really use as much as you want.
Hop Statistics:
Alpha Acids: 10.0 – 14.0%
Beta Acids: 4.5 – 7.0%
Alpha-Beta Ratio: 1.43 – 3.11
Cohumulone: (% of alpha acids): 24 – 30%
Total Oils in mls per 100 grams dried: 1.9 – 3.0
Similar Hop Varieties: Nugget, Columbus, Horizon