Clockwise from the top: Nike Free 3.0 (early version) cut open more than most to form a 'running sandal', Saucony Hattori, NB Trail Minimus, Nike Free 3.0 and the non-minimalist Hoka.

I cut open the toe box of nearly every shoe I run in to prevent blisters. I also believe that my feet move more naturally with an open toe box.

1 Instructions

Mark the line you want to cut with a marker that will show up clearly. Mark around where your toes touch the sides and/or top of the shoe. Err on the side of cutting too little as it's easy to remove a little more later.	Make the initial cuts with a sharp knife.
I use short, sharp sewing scissors for this.	Here's the finished result

2 Downsides

There are some downsides to cutting open the toe box.

You can't return shoes you've cut open.
It's rather disconcerting to cut open shoes you've just paid a lot of money for.
The shoes can rip open because of the extra stress of the cuts. However, in the thousands of miles I've been running in shoes cut open, I've only had two pairs tear and then only after a lot of miles.
You can get debris into the shoe. I've only found this to be an issue when walking, not running unless I'm running through long grass.