Presta valve cores.

[Mikerb]

Something new for me but maybe not to others is the need to carry spare valve cores in my emergency repair kit.
I found whilst topping up the sealant on my tyres that quite often the valve core gets increasingly gummed up to the extent that it could prevent re inflation out on the trail.
I now carry a couple of spares on a ride but also plan to routinely change them occasionally.

 

[fenwick458]

Yes i've noticed this too. had an issue when trying to top up whilst out on the trail, couldn't get the valve open without it unscrewing the entire valve core as it was gummed up, so just had to limp back with a soft tyre and eventually got it open with pliers and core tool, no way was it a finger job
another reason to ditch tubeless IMO, I've done a fair few rides with my Tannus armour and a tube in and it feels spot on so far and I really can't see how that can go wrong (famous last words)

 

[Mikerb]

I carry a valve removal tool as well.

 

[steve_sordy]

I leave my bike overnight with the valves at the bottom of the wheel. This does not totally stop the valve from clogging, but it extends the time when it does. Because I always check the tyre pressure before every ride I would notice when the valve starts to become clogged. It also means that I notice when the sealant needs topping up, because the tyre needs more air.

 

[Tim1023]

I carry a valve removal tool as well.

The muc-off valves are mostly for bling, but they do include a nice valve removal tool as part of one of the dust caps: