Quetiapine
"I've been taking a very low dose of Seroquel (1/2 tab, 12.5 mg I think) off and on for several months now, for anxiety, depression and insomnia (off-label).  It is the most effective sleep inducer I have every taken.  The problem for me is that the effects lasts for about 36 hours, not just 8!  The whole next day is low-energy, although it is also low anxiety.  So it is good when you absolutely need to recover sleep or take a break, but I cannot use it on a regular basis at all and continue to function at work etc."