I have a US visa in my passport which I had to use for work which runs out in 4 years time. If I go on holiday can I just show the visa and go through the US channel or do I still have to queue with everyone else to clear immigration? TIA
You'll find that there will be queues whether you use the US citizen line or not. It's just that one sometimes moves a little quicker.
However if your not a US citizen or Permanent Resident (certain visa holders like the I-551 Green Card) then do as Heathfield has answered.