Hatigarm

so... any good tips for him?

Junk him. Hatigarm is horrible.

Take advantage of the fact that he has two HD slots, meaning two more parts with stats and slots, and four accessories total. Default arms are horrible, swap them out for something smallish and give him a bazooka, 8-vulcan, accelgun, or scouter/raid rifle. His LG melee is...bad, to say the least. Tune for >30 wlk, then pump tec after.

If it is not Hatigram Machine it sux.
It is one of the worst manly melee bots available.

Hatigarm doesn't spam core weapon/ isn't a tank/ doesn't insta win as a land, so you'll have to actually play intelligently for a change. You can keep him stock, or put arms on that can hold things and work from there into making a gunner.

If your playing vanilla, then it's hit and run, poke people with the guns, tackle people who don't know your around. With both core upgrades, the tackle hits rather hard on anyone, really puts the hurt on art units, and it has a wide hit-box. If you tackle someone while they have a wonderbit out, you'll generally destroy it out right and still slam them. The tackle itself has mean knock back, so you can use it to push people in to corners or hazards. The problem with hatigarm is that his play-style of run and gun (with opportunistic core tackles ) isn't viable on a lot of maps. Making him work in volcanic heaven is a pain, but in deep forest you can pick your battles and exploit the terrain for effectiveness.

One thing you should notice is that hatigarm has quite a bit of capacity. If you don't change parts you can fit 5 ability carts on him and still have space for a little tuning or tinkering. That also means that if you do change parts, you have a lot of starting options.

Hatigarm is a big fat hit-and-runner, which is probably why he's made in the image of a big bad wolf.

Your best bet for using him well is to sneak around to the enemy PS(if garm has sniper sight/stealth system I'd get one of them, I don't know cuz I don't own one) and divebomb any healers(if nothing else comes out of your assault, make SURE that you break their repair bits) and critically damaged bots, which if you aim the tackle correctly will net you a kill or two, depending on how badly the damaged bots are hit. You can then continue your attack or beat a hasty retreat to friendlier forces.
You can also strafe enemies with your embedded guns, but the guns are terrible at dealing out serious damage. They're better for quick attacks, supporting fire, or perhaps scoring a quick kill on a critically damaged bot trying to flee battle.

Like Intet said, Hatigarm's stock playstyle is difficult to use on a lot of maps. Wide open maps with either 1)ways to sneak around and catch enemies off-guard, healing, or etc. or 2)The ability to move more freely and easily retreat when damaged are best for a Hatigarm.

You can also put on actual arms instead of doggy-AMs and make the big bad wolf-bot a strafing gunner.

If you play stock, tune like a regular LND, except pump in more TEC instead of STR. Don't lose too much STR though as his Garm Tackle can do serious damage to unsuspecting ARTs.

If you're playing gunner, tune for MORE TEC. You won't use too many Garm Tackles, although they will still be useful if you come up against a heavy ART.

Hatigram is a fun bot to play. My setup for him are some regular arms with a viper shield and a vulcan. He's a good counter for those pesky Vanguards because of his stopping tackle. After you tackle and the opponent gets knockbacked/stunned, shoot and repeat. The only problem is Hatigram will be hard to use if you're fighting 3 or more people at the same time by yourself, but then again, that's a problem in itself

Rule of thumb is one tackle to get you into the action, and one to get you the hell out. Do it right and you'll still get 2 hits in. It's essentially a LND float dash forward that does damage, useful for covering ground and, as I've said before, getting the hell out of there.

One common mistake is most people use him like a berserker,which is wrong because he is horrible bad at tanking

Unless you get H Machine though.