$1 Walmart knife
It has a hole for a lanyard. The blade has a little knob that allows one-handed opening. The spring is attached with a screw, so it can be adjusted or replaced. The serated blade is, well, just that. I wear 2 knives when I'm sailing. My other is a West Marine job that has a marlinspike and a blade. That spike came in handy during a storm last summer! I'm never without it.