From documentation:
-Include
Retrieves only the specified items. The value of this parameter qualifies the Path parameter. Enter a pa
Including \* at the end of the path should work around the issue
PS C:\logfiles> Get-ChildItem .\* -include *.log
This should return .log files from the current working directory (C:\logfiles)
Alex's example above indicates that a directory with the name foo.log would also be returned. When I tried it, it wasn't but it's 6 years later and that could be from PS updates.
However, you can use the child item Mode to exclude directories I think.
PS C:\logfiles> Get-Childitem .\* -include *.log | where-object {$_.mode -notmatch "d"}
This should exclude anything with the 'directory' mode set.