Since you guys love to complain about how overpowered mechs are, I've written up a little guide on how to kill them efficiently and effectively. Split into infantry tactics and mech tactics.

Weapons with anti-mech capabilities:

• Gatling gun (altfire)
• Mass Driver (altfire)
• Gauss rifle (altfire)
• Plasma cannon
• Bazooka (primary fire)
• Chem spray (Primary Fire)
• Flamethrower (Primary fire)

As a mech

Juggernaut: Take a Wolverine and fire the LRMs when it stops to shoot at you. Remember to keep moving at all times and fire the pulse cannon while your LRMs reload. It'll go down surprisingly fast provided it doesn't directly hit you with a mini-nuke. Titan: Same strategy, but you can usually survive a direct hit from the LRMs. Stay at medium to long range since the flamethrower is devastating. Just hide while the LRM reloads and keep using that. If things get ugly, you can usually outrun the titan. Madcat: Buy a Titan if you can afford it, but you can beat these with a Wolverine as well. Stay out of the way of the PPC and you should be alright. Attempts to run will probably be met with minigun fire, so don't be afraid to GTFO if your health goes under 1000. Wolverine: Hit this thing with as many of your 10 or 20 LRMs as possible. PPC is effective if you can pull a direct hit. Raven: Not too difficult. Follow its movements and fire your LRMs ahead so that it runs right into it. Orca: This is probably the hardest to kill, but it does the least damage. If you're in an open area, use the minigun if you can. In an enclosed space, like the tunnels in AOW04, aim your LRMs up and down and hope the splash hits.

As an infantry

Juggernaut: Use a plasma cannon or a mass driver. Circlestrafe while firing Mass Driver alt-fire or plasma cannon primary fire. Keep in mind that this is the slowest and most dangerous mech. The mini-nuke takes a while to reload, so be careful if you haven't seen it in a while. Keep moving and jump/crouch so it's harder to gauss you. Titan: Get fire proof from your local utility guy and/or powerup crate. Plasma cannon primary fire and mass driver alt fire are effective, although dodging is possible. Stay back and use the gauss rifle alt-fire if you have one. Watch out for the 80mm cannon, it can usually kill you in one direct hit and is faster than the mass driver. Madcat: Strafe to avoid the PPC and don't stop firing the altfire of the gatling gun. One direct PPC hit can end you and it usually reloads shortly after the LRMs are fired. The dual miniguns are very inaccurate, so long-range combat is recommended. Wolverine: The pulse cannon is very powerful against Infantry, so watch out since it fires while the LRMs reload. Ambushing from behind with a Mass Driver works well, but I recommend the gatling gun altfire since it's harder to notice than the gauss rifle or the mass driver. The minigun on this is fairly accurate, so medium range combat isn't very effective. Raven: The LRMs don't do very much damage, but the AC2 certainly does. Also keep in mind that the Raven is the fastest mech so it can evade projectiles at medium to long range. It stomps like all the others, but does very little damage so you can usually survive. The plasma cannon takes this one down in 2-3 direct hits so blast away. Remember that if a player uses a Raven, they usually have the AC2 grease so don't rely on that locking up. Orca: Due to its flying nature, this one is hard as hell to hit with projectiles. Use either gatling gun altfire or gauss rifle altfire. If you are in a tunnel and run around a corner and see this, take your best shot and run like hell. The machinegun and its stomping damage will kill you incredibly fast. Backpedal while shooting the gatling gun altfire and you should take it out fairly quickly. If you can successfully hit it with the Mass Driver altfire it'll die in about three hits. Plasma cannon can take it down in 1 hit but you have to hit directly and have the power of RNG on your side.

Edit: added warning about Titan's flamethrower and the chem spray and flamethrower to the list of anti-mech weapons.

Stickied, as this is good info.

My Tactic to kill a Juggernaut is to rush it and use flamethrower. For Madcats, I use suicide ravens

well i use jugg as an anti mech.. i mid-close range mini nuke the opposing mech, that way they cant dodge my nuke and if they are a light mech their done for the day. i have the strange ability of being able to dodge with a jugg...

What I do against juggernaut, Is that I usually avoid infantry combat due to their sniping nature. However I will go infantry if I am a high rank, so I can survive atleast 1 heavy gauss slug. Otherwise, I will be a titan usually, since it's shells are very effective against juggernauts in higher distance. LRM's are for medium range, and the flamethrower is actually extremely devestating in close range.

Against other mechs or against juggernaut with me having high rank and armor, Is a plasma cannon. Extremely devestating against mechs...
The Orca VTOL Is probably one of the trickier.... I usually avoid open areas, and Go via tunnels
I use homing missiles, GaussRifle or Gatling altfire against them... Not so hard to take out, but can surprise you preety easily.

Orcas like to come low to try to crush infantry. If you see it early enough and run backwards with it, you get two massdriver shots before you take crush damage. Can't tell you how many times I've downed an orca this way and I prefer them to try to do this to hovering above me where it's harder to hit. Most times, at that range, it only takes two massdriver shots to take one out.

Ravens like to run you over too. Pot shot with massdriver, running backwards as soon as you see them and try to abuse their field of vision by putting obstacles between you and them that they may not notice to slow them down a little. Finding somewhere to hide and shoot at them should be your priority, so have somewhere to run to in mind as you run back whilst shooting. Remember that they can't jump, but you can!

Plasma cannon one shots orcas or if it doesn't it has extremely low health left.

Orca vs orca, try not to use the rockets if you're close because you take splash damage from your own rockets from the other orca! The guns are more useful but getting the first few shots in with rockets if you haven't been spotted gives you the upper hand. Listen to the engine sounds of the other orca too. When it's stuttering, it's almost down, so don't retreat if you've got a bit of health left.

Orca vs any other mech, you can fly, they can't, abuse their field of vision and fly from infront of them to behind them, going over them whilst shooting rockets. It's harder for them to track you than it is for you to hit them since they're practically stationary compared to you. It might not damage them enough to kill them, but if there's infantry around, you've got its full attention so keep evading and take pot shots with rockets because you have a better chance of surviving than infantry does and they'll be looking too high up to notice infantry. Surprisingly with a bit of luck you can take down any mech with an orca, but it's not as easy to do and requires you to have a lot of space.

I mostly use the Orca VTOL to take out the infantries. I can easily keep my distance and shoot them down with the machinegun fairly quickly. Also, if the Orca's health is running low, I usually attempt to crash-land the Orca on the infantries. This will cause some heavy splash damage to the infantries, as well as killing a few of them, and any 'Mechs that are near the crash site will also take damage.

Laser chaingun I often use to distract a mech, while the damage is not significant the constant *pings* will get the pilots attention. Also at a range you can still be semi-accurate with it. So in short use the laser chaingun to distract a mech while you're buddies take shots at it with mass drivers.

If I'm all out of money and we are gonna die anyway, what is the best free class to go after mechs with while I wait for the game to end?

My gut feeling is that any free class will just make the enemy stronger, since there's bounties and XP.

The closest I can think to cheap mech killing is the SSG, which only works against the Orca (as it's weak with 1000HP), and even then only effective in point blank range, which kinda implies suicide. Add $200 more and you can buy Minigunner which takes Orcas and other mechs down more effectively.

Minigunner's the cheapest without being useless. That's about it.