Great idea!
As others have said, I think my main challenge with grounding techniques is not identifying the need to use them quickly enough. So then it's a massive challenge to ground myself when I'm full on dissociating and don't even know it or when I'm having full on panic/anxiety. But if I can catch it early enough and take some action, I have a few things that seem to help.
For spaciness/full on dissociation:
Top one is smells - that tends to be the sense that gets me back to the present more quickly than anything else.
In therapy - she uses a room spray, which she sprays before I go in. So if I'm getting a bit spacey, I sometimes ask if she'll spray it again. It's quite a strong, floral smell which has reassuring/comforting associations for me.
In public - a spritz of perfume for a quick refocus or a sniff of essential oil (black pepper - not a smell I particularly like so it's better for more spaciness/dissociation as it jolts me back when I'm too far gone to notice the smell of my perfume that I wear all the time) is unobtrusive and looks like fairly "normal" behaviour.
At home - I have the same room spray as my therapist, which I only really use for grounding because of the reassuring/comforting connection - so it's really for feeling more present but also for soothing.
Other ones are:
Washing my hands - spending quite a long time doing it, usually with very cold water.
Putting on hand cream - because it forces me to feel my hands. Works well for fairly light spaciness and is good for being out in public because it doesn't look like a strange thing to do. I massage it in fairly firmly - if I do it too gently/hypnotically, there is always the chance that it will feel too soothing and make me more trancey!
Having a shower/bath in water that's as hot as I can stand.
Shower generally works very well every time.
Bath is sometimes good but can sometimes backfire and I sometimes end up dissociating in there!
Stroking one of my cats is also grounding - I have two and one of them in particular always comes and gives me a nudge if I'm dissociating. Literally, a head butt. So then focusing on her makes me more present.
I also have a song, which if I'm feeling spacey and numb when I'm out and about, I can listen to that. It's lively, fun, has good connotations for me. Not at all a great song or my favourite song - it's a bit of an embarrassing song choice! But for some reason, it seems to really work for me. Even if it means listening to it on a loop for 20mins!
Drinking cold water.
Going for a walk and focusing on my breathing and feeling my feet on the ground. And possibly listening to the song I mentioned above as I walk.
For anxiety:
I find grounding during anxiety more difficult as I think I generally wait until it's so far off the scale that I then can't really ground myself!
Diaphragmatic breathing exercises are probably the best thing for me to do anxiety-wise but if I'm needing to practically peel myself off the ceiling, I probably wouldn't be able to calmly come up with this idea and to sit quietly and do it. Mild bubbling of anxiety - the deep breathing definitely helps.
And going for a walk can sometimes help too.
And taking a bath/shower is also a good one. In the bath, I'd spray my therapist's room spray, throw a heap of magnesium salts in the water, put my bath sound track on (soothing stuff - not my dissociation song!) - and I set a timer in case I overshoot in the wind down stakes and end up dissociating! ;-)