Worst MS product would have to be the crap 'Microsoft' baseball cap I got with my student subscription (about a million years ago now)..  it was black with a hugh 'Microsoft' logo on the front...   rarest thing I've ever had the unfortunate privilege  of owning.

Software wise..  Win98 & WinME sucked, and I'm not too fond of the old SQL2k ent manager

Fav program would be Visual Studio