Unmodified Clipboard content

The following works for Windows borrowed mostly from here.

Needs["NETLink`"];
InstallNET[];
LoadNETType["System.Windows.Forms.Clipboard"];
LoadNETType["System.Windows.Forms.TextDataFormat"];
System`Windows`Forms`Clipboard`GetText[System`Windows`Forms`\
TextDataFormat`UnicodeText]

For completion here is how you do it in linux.

Import["!xsel --clipboard","Text"]

And lastly OSX I haven't tested this on OSX yet but believe it should work.

Import["!pbpaste","Text"]