I've taken a different approach with my keychain. On mine I carry the following:

• Keys
• Leatherman Squirt PS4
• 4Sevens 120db Ti whistle
• 4Sevens ReVO in a leather sheath

I do carry a small amount of duct tape, a split pea lighter, and a compass as part of my minimalist commuter kit in my laptop bag. I carry a pen separately as well as having a few in my bag.

The PS4 is incredibly useful, well as filling the bottle opener, can opener, nail clipper, and backup knife role in addition to the obvious. I use it frequently. The ReVO is the best 1xAAA flashlight I've found, and it makes a great backup to my primary EDC flashlight.

The chances of me needing firemaking while commuting are slim to none but the split pea lighter is so easy to carry I threw it in the bag. If I felt like I needed firemaking on my person the split pea is smaller and easier to use than a firesteel plus tinder.

My keychain carry is customized to my needs, so please don't take this as criticism.