Hougen Manufacturing's portable magnetic drills include the low-profile

HMD150 for tight spots, the HMD505 for versatility, and the HMD 904 for its midrange holemaking capacity.
In addition, the company offers its new 14,000 Series Holecutters that produce large, almost burr-free holes in sheetmetal.
http://www.americanmachinist.com/304/Issue/Article/False/8514/Issue