Bugs for sure
Easy leaveYou are tired of 4 retards ruining your game? You make whole game by youself but they are not deserved to win it? If you leave, they will unlock your items and could still win. Use -disablehelp option to protect your items! Nobody can pickup your items with -disablehelp enabled. Only issue is somebody able to understand — he can transfer the item through your hero directly to his hero. But that requires time.
Emergency exitPhantom Lancer can use Doppelganger out of map border and crash the game with it. It may be tricky, and you probably need to move your camera with Ins/Del buttons.
My rapier (or gem)!You can protect your Gem or Rapier from being used by anyone else. Only restriction — it works at fountain areas, but no worry — it's pretty big. So, if you definitely gonna die, use -disablehelp and suicide next to fountain. Nobody will ever pickup dropped item, but you.
My rapier (or gem). Saga.If a courier dies, he doesn't drop any item (if he wasn't broken and then it drops everything and never ressurects again). So, you can pickup rapier or Gem with it and safely transfer it to your base within 3 mins.
Grief the game with KotLOld abuse with Kotl and Recall — moving your dummy allies onto cliffs. Command -disablehelp helps partially — it locks Kotl from direct targeting. But you can target the ground nearby the real target no matter what!
A wise guyBatrider can easily detect invisible units or the real hero between illusions. Napalm shows number only over the real hero, no matter if he is visible or not. Use it to detect assassins!
Burn, baby, burnUrn of Shadows triggers Napalm damage just like normal attack. This trick allows Batrider to incinerate the target twice as fast.
Greater ChargeBarathum doesn't care about enemy's Linken's Sphere. His Charge of darkness doesn't go into cooldown when wasted on Linken, which allows to dispell spell block from whole enemy team and still get the target to run onto.
Sold, but not deliveredSelling Linken's Sphere won't stop it from applying the buff on the carrier again and again like it's on the inventroy. This way you can get free slot. Note: you have to lose buff at least once in order for this to work, dying or getting the target of enemy's spell.
Dry them outSniper's Shrapnel allows to dispell any big heal from enemy even on level 1. All you need is to hit enemy with animation (scatters debrei) of falling.
Silent dangerLearning Clinkz Searing Arrows while being Windwalked allows to attack enemies with right click without breaking invisiblity. Works only for the duration of this Windwalk and only for right click.
Attack them while they're hotAxe, Centaur, Shredder, Legion, Tiny — all of them have passive abilities which reacts on attack event. Issue is, orb attack doesn't count. You can beat the shit of any of them, using hotkey attack on Viper/Silencer/etc, without fearing of passive.
I like when you (don't) hit meThe more you trying to stop the attack while being Duel'd or Aggro'ed by Axe, the more passive procs you triggers. And please, if you are playing support with zero damage, DO NOT attack those heroes if they caught your ally. You only make it worse (or maybe it's what you want?).
I don't care about your rulesReality Rift ignores Spell Block and always shifts positions of the target and the caster.
Poisonous DazzleDazzle's poison counts as stun and prevents most triggered abilities from channeling. For insance, Charge of Darkness or Sun Ray of Phoenix. A single point into this skill is enough to stop such skills.
Disable the shit out of themStatic Storm of Disruptor, upgraded with Aghanim's Scepter, disables evasion, critical strike and damage block from every affected unit. Same happens under the Doom or Duel. Kill them easily!
DoomYou can not deny any ally under the Doom's ultimate, unless if it's upgraded with Aghanim Scepter.
Poisonous Dragon KnightDK's poison from Dragon Form works on every object, including wards. But some stuff bugs out because of this, for instance — you can't destroy Pugna's Ward. It heals back!
Be silentGust harshly locks out it's victims, preventing them from any movement. Enemies cannot dagger out — they'll be returns to original position.
Hawking's awardEnigma's Black Hole can't stop units from using instant orders like items. You can get youself onto Eul to avoid damage or use Shiva to deal the damage.
Long jumpsVoid can jump 2x as far if tree is targeted with Time walk. You have to be precious though, pointing to the very center of tree. Using Phase Boots right after jump allows to decrease accuracy.
Slide to unlockYou can move hell a long path on the border of the map with Slark. Use Pounce with proper facing angle, and you'll travel half of map.
Kill it with magic?Passive ability of Huskar recounts it's bonuses every 0.5 seconds. Placing whole magic damage into a single 0.5 window allows to penetrate him easily.
Diabolic WastedExplosions of Leshrac triggers onto invulnerable units (under effect of Eul, for instance), wasting damage.
Chain of fingersLion's Finger of Death, upgraded by Scepter, turns into Chain lightning with 16 max targets and small jump distance. You don't have to pickup enemies into pile for ulti — just make chain of them!
Laguna GibLina's Laguna Blade with Scepter deals the damage instantly, without 0.25 delay like normal ultimate. This damage ignores target's spell resist as well and cannot be improved by Ethereal state.
Chieftain still biggerAny stun, following after Chieftain's Stomp, will turns a sleep effect into stun. Basically you can make stun for 5 seconds long, if another stun will be applied onto stomped enemy within 0.65seconds after that. You can easily do that with Ogre, but thats pretty much wacky combo.
Open wounds, closed eyesLifestealer's Slow doesnt' work on invisible of fogged units. It cannot be dispelled either, no matter which dispel tries to do it.
Stone GazeMedusa's ultimate increases any damage received by affected enemies. Pickup pure damage casters and destroy them!
MeePwnBuying back as Meepo with clones doesn't trigger a penalty of gold. It doesn't increase next respawn duration either. As well, Tranquil Boots will follow the main hero's state, no matter what clones do, providing extra regen and movespeed permanently.
MorphingMany buffs and debuffs can be removed with morphing by Troll or Medusa. Yes, Split shot is a morphing ability. Zero cooldown allows to dispel literally everything which is dispellable. Just came to my mind — Naga's armor debuff or Veil of Discord debuff.
Bad morphingChanging hero attack type from melee to ranged or vice versa causes all Manta's illusions to disappear.
Endless HeartSpirit Bear can make use of Heart of Tarrasque and Dagger and never lose it, regardless damage received.
TakenDominating the creep which has been haunted by Lifestealer effectively deletes him from the game. Lifestealer able to get out only if he has contol over the unit or if unit dies.
Priceless hide and seekPuck won't get bonus assist gold and experience if he stais in Phase Shift while kill happens.
Hidden dangerKilling the unit while he is hidden with Shadow Demon's Disruption (killed by poison) or OD's Astral Imprisonment (killed by Sanity's Eclipse) effectively ignores any reincarnation ability he has. Useful to kill Leoric or Aegis bearer. No reincarnation will be wasted as well.
Orb-walkingBuying orb-attack with lightnings or Desolator on the melee hero will grants him twice as much lifesteal from Vampiric Aura. 60%!
Strong StormStorm's passive ability removes Linken's Sphere buff from the enemy on triggering.
Spilling attackLanaya's Psi Blades deals pure damage, effectively blocked by Pipe's Barrier or spell immunity.
Sapper chickenGround courier doesn't receive damage from Techies' land mines, but triggers them. You can demine whole ground with it.
Suicide issuesSuicind with Bloodstone while playing on Techies counts as Suicide squad Attack, effectively reducing respawn timer by 50%.
Locust swarmBeetles of Weaver can attack the enemies around them while flying and not latched. It allows to remove up to 50-70 hp from enemy's tower.
Wisp-Maphack (not really)Wisp's countdown on Relocate over the head is visible for everyone and though fog of war or invisiblity as well. It allows to properly time out aoe-stuns. Watch the clock!
Useless projectile evasionDagger or any other skills, which supposed to disjoint projectiles, can't disjoint any triggered projectile. You can't evade PA's dagger or Tinker's missiles. Reason is — code malfunction.
More vision!Buttons «deliver items» and «resume delivery» inside the courier allows to see big AoE around him. Useful for scouting without risking to lose the courier.
Picking up the first runeIf enemy of ally blocks out rune spawn point with his body you can turn camera with Ins/Del buttons and get better angle. Some units pretty fat and it won't work then. Probably you'll have to replace the model with something bigger then.
Weak PC isn't always badLow perfomance PC suffers of FPS drop everytime stomp is casted, including Roshan's stomp. If you suddenly noticed 5-10 FPS drop, enemy could going Roshan.
Vision FrostLich with Scepter can wards enemy's woods with ultimate. Golems are immune to magic and Chain frost always give vision around it.
Arc Warden's issuesCopy of Zet steals experience just like normal hero. Do never keep him nearby while farming or you'll drop behind in EXP.
Regeneration % doesn't stackRegeneration from Slark's ulti, Heart Of Tarrasque, Fountain and Healing ward of Juggernaut doesn't stack.
Manaleak > stormMana Leak works on invulnearble units, making Kotl proper counter to the Storm. Only theoretically, of course, in real life Storm melts him down easily.
Safe Sun RayGem doesn't work while Sun Ray is enabled. Transfer it to somebody else if you gonna use this ability.
Cursed goldHand of midas can be wasted on Necro warriors without any effect, but it will start cooldown nevertheless.
ConclusionThere are hundreds of other bugs in official 6.83d, but them makes YOUR life worse, not enemy's. Therefore they aren't worth mentioning. You can find all of them fixed in changelog data of DotA Allstars.