Have the trap not sprung until they are in the middle of the room.
Give the monsters a stealth check for a surprise round. If a PC has Passive Perction high enough to beat the stealth check, they get to act in the surprise round.
Have monsters that can burrow,fly,crawl, phase through/around them.
Also, Think Left for Dead 2. (I actually have a full set of l4d2 heroic tier zombies i've created)
Spitter type Tactics:
Have a mage/monster create a damaging zone just behind the choke point, covering both groups. Acid, fire, etc. Place it such that a way that the defenders in the chock point would take more damage backing out to cover the squishies than running forward into the cave, leaving an opening for skirmishers to slip in.
Smoker type Tactics:
I seem to recall in one of the MM books a bug that has spider slimb, uses a sticky tongue thing, and can pull. Have one or too of them on a ledge over looking the choke point to drag the defender away and let brutes/skirmishers whack on him. Also, if high enough cave, wait on cieling and pull upwards into the air. Now your brutes and soldiers can pass underneath, and if ranged support kills the bug, defender takes fall damage / lands prone.
Charger type Tactics:
Unfortunately, there isn't anything I've come across that replicates a charger very well, other than what i've created myself. Closest thing is push/pull/slide effects for monsters. Traps on the other hand... Add an Indiana Jones Boulder rolling down the choke point. On a hit, do damage and push target 2 squares, on miss, half damage, push target 1 square. Follow up with Skirmishers.
Horde:
Lots of minion skirmishers. Especially if they have spider climb.
Add some player powers to an evil wizard as an encounter or recharge 6, such as Flaming Sphere. Roll that towards the choke point and see how they run like pigs from a gun (coo coo ga joob). Naturally, follow up with skirmishers.
Use swarms. They can move through the defenders, or just make standing in the choke point uncomfortable, as well as limit the damage potential from melee defenders and ranged weapon players until they use bursts. Fun thing about bursts, they often like to target creatures instead of enemies, meaning your defenders need to get out of the way. Enter skirmishers.
Charging Gelatinus Cube! (or anything else with engulf) Eat the defenders!
Rope swings. Have enemies on cliffs holds ropes swing over the defenders and drop down. Have them make an athletics check to swing twice thier move as a move action and drop (fail and they move normal and drop). Make an acrobatics roll when they drop. Succeed, mitigate falling damage and land on feet, fail, take normal falling damage and land prone. They are now behind defenders. works well with skirmishers, add a brute to keep the defenders seperated from the squishies.
Add 10ft+ pits and use with the Horde strategy. Think 300. Wall on one side, pit on the other of the choke point. Every chance you can, have a minion charge and bull rush, trying to push the defender into the pit. with 8 minions, you will have several chances per round, and eventually it will pay off. once the way is clear, charge your monsters in while defender is in the pit.
Add attractive fantastic terrain, such as Blood Rock or a Font of Power or a Sacred Circle in the middle of the room. Hopefully you can entice your defenders out of the choke and into the open. Or use Blood rock for your artillery, and now they have to enter just to get him off that tile. Be descriptive, saying "you notice tendrils of red, blood like energy writhe up from the blood red rock at the kobold archer's feet and infuse his bow". Now the players have an idea what is going on, and will covet that square. Place one 2 or 3 squares past the choke point to entice on the of ranged strikers to come forward and take that square.
Have players trained in dungeoneering make a medium DC check to notice a Rock Slide trap that would be benificial to the players, but they have to come out and be adjacent to the trigger. Have artillery minions on a too high ledge that either get crushed, or the ground falls out beneath them and they come sliding down. You lose the artillery minions, but now you have unprotected party memebers in the open.
Staggered encounter. You have your goblin brute, artillery and minions inside the cave. After 1 or 2 rounds, a patrol/returning raiding party approaches from behind with a soldier, a skirmisher, and more minions.
Domination! Nothing says fun like forcing the defender to charge backwards at his party and make an MBA or bull rush into a pit
Doesn't even have to be full domination, find a monster with the charm keyword that makes the target take a whack on someone else (Duergar Cleric of Asmodeus for example). They will now spread out a bit, leaving openings. You could even target the ranged striker hiding in back and make THEM shoot the defenders for lols. "Sorry, my hand slipped?".
3D terrain. Sure you have a choke point, but it's on the ground level. things on the ledge above can run around and drop down behind the choke point. Make sure there are ladders beyond the choke point for the players to climb so they can get at those nasty artillery shooting fish in a barrel. That forces them to also leave the safety of the choke point.

Give the monsters a stealth check for a surprise round. If a PC has Passive Perction high enough to beat the stealth check, they get to act in the surprise round.
Have monsters that can burrow,fly,crawl, phase through/around them.
Also, Think Left for Dead 2. (I actually have a full set of l4d2 heroic tier zombies i've created)
Spitter type Tactics:
Have a mage/monster create a damaging zone just behind the choke point, covering both groups. Acid, fire, etc. Place it such that a way that the defenders in the chock point would take more damage backing out to cover the squishies than running forward into the cave, leaving an opening for skirmishers to slip in.
Smoker type Tactics:
I seem to recall in one of the MM books a bug that has spider slimb, uses a sticky tongue thing, and can pull. Have one or too of them on a ledge over looking the choke point to drag the defender away and let brutes/skirmishers whack on him. Also, if high enough cave, wait on cieling and pull upwards into the air. Now your brutes and soldiers can pass underneath, and if ranged support kills the bug, defender takes fall damage / lands prone.
Charger type Tactics:
Unfortunately, there isn't anything I've come across that replicates a charger very well, other than what i've created myself. Closest thing is push/pull/slide effects for monsters. Traps on the other hand... Add an Indiana Jones Boulder rolling down the choke point. On a hit, do damage and push target 2 squares, on miss, half damage, push target 1 square. Follow up with Skirmishers.
Horde:
Lots of minion skirmishers. Especially if they have spider climb.
Add some player powers to an evil wizard as an encounter or recharge 6, such as Flaming Sphere. Roll that towards the choke point and see how they run like pigs from a gun (coo coo ga joob). Naturally, follow up with skirmishers.
Use swarms. They can move through the defenders, or just make standing in the choke point uncomfortable, as well as limit the damage potential from melee defenders and ranged weapon players until they use bursts. Fun thing about bursts, they often like to target creatures instead of enemies, meaning your defenders need to get out of the way. Enter skirmishers.
Charging Gelatinus Cube! (or anything else with engulf) Eat the defenders!
Rope swings. Have enemies on cliffs holds ropes swing over the defenders and drop down. Have them make an athletics check to swing twice thier move as a move action and drop (fail and they move normal and drop). Make an acrobatics roll when they drop. Succeed, mitigate falling damage and land on feet, fail, take normal falling damage and land prone. They are now behind defenders. works well with skirmishers, add a brute to keep the defenders seperated from the squishies.
Add 10ft+ pits and use with the Horde strategy. Think 300. Wall on one side, pit on the other of the choke point. Every chance you can, have a minion charge and bull rush, trying to push the defender into the pit. with 8 minions, you will have several chances per round, and eventually it will pay off. once the way is clear, charge your monsters in while defender is in the pit.
Add attractive fantastic terrain, such as Blood Rock or a Font of Power or a Sacred Circle in the middle of the room. Hopefully you can entice your defenders out of the choke and into the open. Or use Blood rock for your artillery, and now they have to enter just to get him off that tile. Be descriptive, saying "you notice tendrils of red, blood like energy writhe up from the blood red rock at the kobold archer's feet and infuse his bow". Now the players have an idea what is going on, and will covet that square. Place one 2 or 3 squares past the choke point to entice on the of ranged strikers to come forward and take that square.
Have players trained in dungeoneering make a medium DC check to notice a Rock Slide trap that would be benificial to the players, but they have to come out and be adjacent to the trigger. Have artillery minions on a too high ledge that either get crushed, or the ground falls out beneath them and they come sliding down. You lose the artillery minions, but now you have unprotected party memebers in the open.
Staggered encounter. You have your goblin brute, artillery and minions inside the cave. After 1 or 2 rounds, a patrol/returning raiding party approaches from behind with a soldier, a skirmisher, and more minions.
Domination! Nothing says fun like forcing the defender to charge backwards at his party and make an MBA or bull rush into a pit

3D terrain. Sure you have a choke point, but it's on the ground level. things on the ledge above can run around and drop down behind the choke point. Make sure there are ladders beyond the choke point for the players to climb so they can get at those nasty artillery shooting fish in a barrel. That forces them to also leave the safety of the choke point.
