Different sort of attack
This is more the sort of attack that I am used to getting. They use non-printing characters to try and trigger something.
[Wed Dec 30 22:29:03.786013 2015] [core:error] [pid 1091:tid 2814376768] [client 184.108.40.206:60507] AH00126: Invalid URI in request x8e x94|xf7xb4xb6xa8xb7xbfx99xd3Qxf7xa1
Probably something nicely crafted to break an older webserver.