Since this site is mainly oriented to tactical simulations and training, it might be fitting to include a section on tactical gear in general. To the purist, the word tactical doesn't describe your equipment; but rather it describes what you do with your equipment. This is true, but there are certain items that lend themselves to tactical use more easily than others. This page will cover some items that are handy for indoor tactical CQB.
Balaclava (hood) - this is a nice item to have for indoor CQB, especially for Airsoft. It will protect your face, ears, and neck from hits at close range.
Gas Mask/Goggles - Eye protection is absolutely essential for Airsoft combat. At the very least you should wear protective goggles of some sort. The gas mask is an optional extra to add more realism to certain training exercises. If you've got gas masks available, try running a couple scenarios with them on. Unless you have a heart condition or asthma. Tactical CQB can be strenuous enough as it is, and a gas mask only makes it harder to breathe. Use your judgement.
Tactical Holster and Secondary Weapon - An absolute must. For CQB you don't want to get stuck with an empty or malfunctioning primary weapon. Your choice of pistol should be one that you are comfortable with and can shoot accurately. A spring pistol will usually suffice, but a gas blowback is handy. As far as holster selection goes, make sure it's a sturdy model that will retain your pistol under any circumstances, and yet doesn't require a lot of time to draw from. Pictured here is a standard military belt holster, but tactical thigh holsters are also a good way to go.
Primary Weapon - This is the central piece of your CQB gear, and most of your other gear will be added based on your choice here. Just about any compact automatic weapon will work - the MP5 series is popular. You can use rifles, but I personally would not take anything larger than say an M4/XM177/Steyr AUG size package. My usual choice is the MP5SD6, and even that feels a little big at times. You want decent accuracy with maximum maneuverability. A good deal of CQB shooting is instinctive so you probably won't be taking the time to aim with the sights. Therefore extra optics are unnecessary. About the only thing that would be handy here is a tactical light attached to your primary weapon - this will allow you to search dark places and it can even be used to aid instinctive aiming.
Tactical Radio - This is a must if you have a relatively large team or several small teams and need to coordinate the action. The ideal accessory for the radio is a voice-activated headset, but failing that a lapel mic is useful enough. Ideally your team should rely only on hand signals to communicate, but if your team splits up or you've got several units, at least one person on each group should have some for of electronic communications.
Magazine Pouch/Extra Magazines - Definitely necessary. This is all the extra ammo for your primary weapon, and maybe even your secondary weapon. We prefer to keep combat as realistic as possible, so we usually only use standard capacity magazines. This definitely makes extra magazines a must.
Tactical Sling - Also a must for your primary weapon. If you have any failures with your primary, you can sling it and use your secondary. You can also use certain slings to hold your weapon level while you reload it with one hand, and cover yourself with your secondary weapon in the other hand.
Elbow/Knee Pads - These are really nice to have, especially if you follow the philosophy of "train hard, fight easy". These allow you to do things you might normally avoid, such as literally diving for cover.