Laura posts a weekly Zentangle challenge on her blog "I am the Diva" (should be a link somewhere on here...) and last week's was to draw using only straight lines. I ended up with two entries.
This first one came about purely from the desire to do a compass rose, and to create the impression of curves using only straight lines. And to use my new colored pens. They're Staedtler pens, this was done on a 4x6 cardstock, and the tangles used were (no idea if there's an official name for the stars and stripes I used radiating from the globe), bucky, nightsbridge (though I didn't know that when I did it.... it is a checkerboard), Hurry, hibred, chard, triangles, and I really have no idea if the last is an official / named pattern anywhere. Again, it's just a grid I've drawn in the past. :)
The second one is just what happened when I started drawing, wanting to use the celtic tri-knot for the string.
This one uses ixorus, chard, nzeppal, and facets. Of the last three, I'm not sure if the center one is a named one or not. I think it's a variation on arrowheads. He honeycomb I don't recall seeing like that before (again, the hexagonal pattern like that is one I've drawn for ages), and I know the last one does have a name, but I didn't write it down.