Contribute your strategies!

Kit: Ninja
Strategy: If you're running from someone, find a ravine and
jump in. Then shift to tp back behind the player and knock them into the ravine.

Kit: Demoman
Strategy: If you're mining in a cave, place demoman traps near the entrance of the cave so players hunting you down will step on your trap and explode.

Kit: Fisherman
Strategy: Use your fishing rod to fish players into a pool of lava or hole where they can die of fall damage.
Counter: Run the opposite direction of the fisherman to get unhooked before you're realed in.

 

Kit: Stomper
Make a tower and break the blocks under you as you stack up to make a invisible tower so you can sneakily stomp on them iron players

Kit: Portal
Put the portal in a pit of lava and send people for a swim

Kit: PickPocket
Steal their wood at the beginning. Steal a lot of iron/soup before a fight

Kit: Jackhammer
Make a 2x2 staircase to bedrock and break wood as players come down. They fall...

 

Kit: Anchor
The way to take care of teams with Anchor is by a ravine. If you place yourself correctly, they will probably try and sandwich you, and with luck will knock each other into the ravine!
Anchor is also a great kit for people with INSANE refills (me for instance) but trashy combos. If you can, you could take on a full iron, and come out on top! Anchor is a good anti-tower kit, just watch for projectiles!
Counter: THERE IS NONE TO ANCHOR.

Kit: Monk: Monk is a very old kit, but not played much nowadays. It can be very powerful in soup but more so in no-soup (ugghh). If you can, put your Monk rod into your hotbar on the 9 slot (or a slot where you are comfortable with it). With this, monk someone after he's eaten 4-6 soups, he might be tempted to refill and you can crit him!

 

Kit: Checkpoint
Place your Checkpoint in a distant swamp; if you're low on soup in a fight, you can just run away for 10 seconds and then safely teleport back to the swamp to gather new soup!

 

Specialist: Get as much XP early in the game as you can. Either run Seoul killing people or find a cave and mine as much as you can, trying to find a mob spawner along the way. Don't bother going to the feast, your enchants are stronger than diamond armor. Enchant your iron armor, which you should have by now, and try to get protection 1 with unbreaking 1. For your sword try to get sharpness 1 with fire aspect and unbreaking. Then go and kill the feast winner and any other players in the game. This kit works well with other people, especially miner, toolmaster, and Souper.

 

Not sure if this is much of a strat, but here:

Grappler: I personally use this a multi-purpose kit. This kit specializes in hunting and fast paced gameplay. I have a few strategies while using this kit:
Hook on to enemies to avoid chasing them for long periods of time,
Hook a nearby block to get away from enemy players,
Use the grappling hook and some blocks to easily get to towers. If you get knocked off, hook on the stem of the tower to avoid the fall damage.

For beginning game structures: See a blacksmith's house nearby spawn? Use your grapple hook to get there as quickly as possible.

Counter Kits:
Ninja and Kangaroo.

Counter Strats:
The good ol' fashioned trap. Make sure it's a concealed space!

Despite all some of these counters, this kit in general is really strong; some may even say over powered.

 

Kit: Fireman
Strategy: You have a bucket and fire resistance (permanently) plus 10 seconds of lava resistance (can be procced as much as you want). What are you going to do?
Yes. Live your dreams...unleash our anger and pour lava in someone's hole! Do it!
Counter: Magma, being fast!

 

Fireman: MLG water over and over again at the beginning of the game and annoying the endermage that keeps mageing you on top of their tower over and over again.

 

My one and only strategy:
Step 1: Spawn and run as far away in any direction as possible.
Step 2: Hide.
Step 3: Shift.
Step 4: If any enemies see me, I try to bargain and begin a friendship.
Step 5: If step 4 fails, fled the scene.
Step 6: Die.
Step 7: Cry in the fetal position for 3 hours.
Step 8: Repeat.