No particular order:
Mike and the Mechanics (insipid middle-of-the road slush)
Michael Jackson (most over rated pop-star of all time)
Michael Ball (non-original, very ordinary covers of very ordinary material)
Michael Buble (as above with a slight Sinatra twist)
Michael Bolton (awful nasal voice, suit-sleeves-rolled-up, (very) bad hair US drivel)
Mike Batt (thanks for the Wombles and Katie Melua)
George Michael (the guy can sing but too far up his own backside for anyone to feel remotely sorry for his continuing predicaments - [except maybe that woman from Eastenders])
Mick Hucknall - except for very early SR stuff, awful bland junk-music, too full-of-himself to be liked...
Rod Stewart - please stop making those awful cover-albums, has become a cartoon-version of himself
All Boy/Girl Bands and other childrens music- a "band" that particularly comes to mind are N-Dubz - doing their bit for neuro-science by sharing a single brane sell