There are at least 7 artists named halo:

1. British Rock band of the 2000's, they garnered much of their initial popularity by the offering of a free EP (Still Here) to all who signed up on their website. That was followed by an album in 2002 (Lunatic Ride), which featured re-recordings of two of the four EP tracks.
When Blake replaced Jim Davey on Drums (2004), the Band became The Vega Method briefly. Graeme Moncrieff, Iain Moncrieff Stevie Yeomans, then joined with John Bevan to form The Exhibition.

2. Halo is mistagged music written for the Halo video games. See also Martin O'Donnell & Michael Salvatori. If this non-artist appears in your charts, do last.fm and yourself a favor. Fix your artist tags.

3. Slovenian rock band formed in 1996 by Danilo Kocjančič (ex-member of popular band from 60's, Kameleoni), Jadran Ogrin, Zdenko Cotić and tulio furlanič (also from Kameleoni. They are most known by the hit single Anita Ni Nikoli.

4. Australian noise and industrial duo with metal influences. Active since 1994, they have toured with Pig Destroyer and Total Fucking Destruction. They have 5 full-length albums: Subliminal Transmissions (1998), Guattari - From the West Flows Grey Ash & Pestilence (1999), Massive Corporate Disease (1999), Degree Zero Point of Implosion (2000), and Body of Light (2003). According to Halo's Myspace new album is coming at 2008.

5. German Rock band which formed in 04 or 05. The hired and fired about 15 singers until they had one which fit their vision of the band. Halo is situated to Mainz on the Rhine river and they are sharing their practice room with the also local band Nemo.

6. An early 90s collaboration between American producers Thomas Penton and Luis Duran.

7. A christian (hard)rock band. Halo released two albums in the early 90's on Pakaderm records and produced by John and Dino Elefante. Simple understandable lyrics and catchy hooks with a strong gospel message, 80's rock with the Pakaderm stamp of approval.