1. %date% and %time%. They expand properly, and are handy for use in log files.
2. %random% will generate a random number, handy for when you're starting some process many times quickly and want to use a log file for each process. 
3. The F8 key completes commands from what you've typed before. No, I really didn't know that before, and yes, I kick myself once per day now in atonement. 

I already knew about set /a, so it doesn't count. (set /a 2+2  prints 4, for example)

How does this relate to Powershell? Well, over time I've accumulated the custom of writing several small batch files that I use in CMD the way Powershell uses aliases. For example, d.bat, somewhere in my path, executes dir /w /on /ad, showing my all subdirectories. dd.bat does the opposite, dir /w /on /a-d, showing me only files. x.bat (x.cmd, anymore) types exit for me, closing the CMD window. (s.cmd executes start ., which opens explorer.exe in the current directory, but I digress.)

I couldn't get this to work in Powershell. set-alias x exit succeeds, as a command, but fails to run:

>set-alias x exit
>x
Cannot resolve alias 'x' because it refers to term 'exit', which is not recognized as a cmdlet, function, operable pro
gram, or script file. Verify the term and try again.
At line:1 char:2
+ xx <<<<

There's another way however - create a function named x, add that to my $profile, and things work like I want.

function x()
{
    exit
}

I want to be able to create and close tasks from Powershell. As I was experimenting with this, it occurred to me that it would be great if each task had a unique number so that I could use that when closing it. I was in for disappointment. Yes, each task does have a unique number, but it's huge!

Example: 0000000054053A5AAF751245878345951938FF0A0700FAA3A5EE761BD9439C9D3980E21B1386000001E07A30000071D3B96BC8BA4C459F0D620C68922A1B0000031D22200000

Yeah… I'm not typing that in Powershell in order to close a task. I also don't want to have to copy/paste the entire title. What to do? I eventually gave up and decided to manually (for now) isolate the characters that seem to be unique among my tasks. Now my get-outlooktasks.ps1 file looks like this:

$olApp = new -com Outlook.Application
$namespace = $olApp.GetNamespace("MAPI")
$fldTasks = $namespace.GetDefaultFolder(13)
"Gathering incomplete tasks... please wait"
$unfinisheditems = ($fldTasks.Items | ? {$_.Complete -eq $false})
foreach($item in $unfinisheditems)
{
    $arrayofentryid = split-string -Input $item.EntryID    

    for ($a = 129; $a -le 136; $a++)
    {
        $smallid += $arrayofentryid[$a]
    }

    $item | format-list subject,percentcomplete,duedate,@{label="Id";expression = {$smallid}}
    $smallid = $null
    $output = $null
}

There's probably a much better way of getting that substring of the EntryID, but I don't know what it is, yet. I'm sure it would be more appropriate to do this some entirely different way, at the very least diffing three or more EntryIDs and finding a contiguous unique range on the fly. Maybe someday I'll bother. J For now, my complete-task.ps1 file looks like so:

param ([string] $pattern)
if($pattern -eq $null -or $pattern.length -eq 0)
{
    "Error - supply a portion of the entry id"
    return
}

"Getting incomplete tasks..."

$olApp = new -com Outlook.Application
$namespace = $olApp.GetNamespace("MAPI")
$fldTasks = $namespace.GetDefaultFolder(13)
$unfinisheditems = ($fldTasks.Items | ? {$_.Complete -eq $false})
write-host Getting task whose EntryID contains $pattern
$tasktoclose = $unfinisheditems | ? {$_.EntryID | select-string -pattern $pattern}

if($tasktoclose -ne $null -and $tasktoclose.count -eq $null)
{
    $tasktoclose.Subject # display the subject at the console
    $tasktoclose.Complete = $true
    $tasktoclose.Save()
    write-host "Task has been marked completed and saved."
}
else
{
    "More than one task returned OR no task found. Aborting."
}

It may not be pretty, but it works!