Modelio - Modelio is an open source modeling tool supporting natively UML, BPMN and model exchange with XMI.
Sketch - Professional digital design for Mac.
Diagramo - Diagramo is an online flowchart software - diagrams (create, edit and share)
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
UML Designer - UML Designer provides a set of common diagrams to work with UML 2.5 models.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.