Removing duplicate values from a PowerShell array

Use Select-Object (whose alias is select) with the -Unique switch; e.g.:

$a = @(1,2,3,4,5,5,6,7,8,9,0,0)
$a = $a | select -Unique

Another option is to use Sort-Object (whose alias is sort, but only on Windows) with the
-Unique switch, which combines sorting with removal of duplicates:

$a | sort -unique

In case you want to be fully bomb proofed, this is what I would advise:

@('Apples', 'Apples ', 'APPLES', 'Banana') | 
    Sort-Object -Property @{Expression={$_.Trim()}} -Unique

Output:

Apples
Banana

This uses the Property parameter to first Trim() the strings, so extra spaces are removed and then selects only the -Unique values.

More info on Sort-Object:

Get-Help Sort-Object -ShowWindow

$a | sort -unique

This works with case-insensitive, therefore removing duplicates strings with differing cases. Solved my problem.

$ServerList = @(
    "FS3",
    "HQ2",
    "hq2"
) | sort -Unique

$ServerList

The above outputs:

FS3
HQ2