kicadpcb
My PCB layout program of choice – Kicad – has footprints for normal rounded solder jumpers; but also triangular ones.
What benefits, if any, do the triangular ones offer? Or is it a purely aesthetic choice? Seems to me that the triangular ones would be more annoying; that they would be more difficult to clear of solder.
In recent versions of KiCad there is a Footprint Library Browser, allowing exactly what you asked for. It can be opened from inside PcbNew via the menu option "View >> Library Browser".
You can do this without a schematic. Open PcbNew and click on 
at the right hand side. This will allow you to add any footprint, such as a 1x1 pin header. Make sure your grid is 100 mil. As a proof of concept, I used the 1x5 pin headers 
.
Best Answer
For the same height of pad, the angled ones provide a higher length of the gap, meaning simply that there's a higher chance to find a random spot where the solder creates an initial bridge, before surface tensions "pulls" the solder to connect across almost the full height.
Also, but this is more speculation than the previous sentence, the concave part might lead to a solder blob is centered at the "dent", minimizing the gap distance, further increasing likelihood of a successful solder bridging.