Or appreciating other peoples perspective, I'll go first:

MTB er (I hate 4 x 4ers)
Walker 😯 (with an L, without red socks. Just grumpy)
4 x 4 (I love making deep ruts and watching cyclists fall off in them)
Dog owner (it wasn't my dogs sh1t, OK?)
Horse owner (I look down on you, get out of my way)

A paltry 5….

MTBer
Climber/Mountaineer (occasional)
Walker

Except none of the above at the mo due to being bloody ill for ages. 😡

Me too Grumm 🙁

it's a bit sad that 'walking in the countryside' is considered 'niche' 🙁

Country and Hill Walking
Biking
Power Kiting (not much in the last 2 years as I want a big new kite but keep buying bike parts instead)

Mountain biking
Fell running
Walking (although the latter is frustratingly slow when you can do the former!)

Bikes
Rocks
Horses
Kites
Boats
Boards
Guns
Boots
Fishing

It's all good!

Dogging 😳

Do a bit of walking up n down hills
Mountain Biking
Ultimate Frisbee (I think that one is pretty niche!)

Beer-making 😛

Ultimate Frisbee (I think that one is pretty niche!)

Second only to 'Total Table Tennis'

slalom waterskiing

bikes
skis
walking (though usually bike)
climbing (dabble anyway)

Horses, but haven't ridden in years now, too costly.

Biking
Powerkiting
Snowboarding
Wakeboarding

At least I don't moan when it's too windy to go out on my bike!!

Motorbiker (I don't give a ****)
Roady (Get out of my way)
Triathlete (wrong gear and can't ride in a group, like to swim in lakes)
Rock Climber (Shirt off in the sun on a rock)
Hill walker/scrambler (Should have gone for the waterproof trousers)
Polo (My horse is better than your horse)

Biking -MTB and Road
Shooting – Clay and Game
Fishing – Sea, fly and coarse
Skiing – and snowboarding.

I hate niches

Bikes-mtb,road,cylo cross,time trials.
Rocks-bouldering and ropes
Horses-hunting and dressage
Boats-rib
Boards-snow,water,skate
Guns-air rifle,shotgun and pistol
Fishing-course.fly and game
kyaks
canoes
running-fell and road
4×4's
motorcross
motor bike trials
skiing-slalom and freestyle.
bush crafty lad too…

thats not bad to say I'm 17 ….