A hand saw lives in my Hydro pack. I can't tell you how much that gets used.
But aside from that, when I'm in full Mt biking mode, I don't normally stop for TMs, I'm more into riding! I'm much more effective at Trail Maintenance when I focus on it. Then I outfit my fatbike with my TM setup: Hand trimmers near my handlebar stem. Small Loppers dangerously tucked into the chest strap on my hydropack (yeah, I know, I know...looking for a safer arrangement). And my saw and work gloves handy in my frame bag. I just ride from trouble spot to trouble spot. Sometimes, having the bike along is an asset, other times it's a liability depending on how bad the area is that needs attention.
I wished more Mt bikers would step up to the plate and put a little TM time in.. This is growing season, so at this time of the year, it's overwhelming to keep up with the miles and miles of trails around this area. Whether you do a rolling TM like I'm doing, solo hike a trail with pruners, participate in organized TM's, saw out an annoying tree fall, or build a logover.. It's all good. Every little bit helps.