Just documenting some stuff my friends and I have found over the course of playing this game since release. See the playlist here:    • Tri Force Heroes - Tips/Tricks/Glitches  

Update (2021/8/18): A mod to disable the communication icon SFX now exists, among other SFX mods, thanks to player Phoenix. The mods can be found here: drive.google.com/drive/folders/1d2wl5q_gTbpTXs_AHg…

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Alright, here's the fun one. In multiplayer coop mode, if one pauses the game during a level shortly after releasing a communication icon on the touch screen, the game will send the icon to the other players every frame the game is left paused.

Yes, other players can see the rapidfire icons, and it does in fact lag the game if it causes too much strain on the server. Please use this one with caution: It's easy to accidentally leave a room!

There's also a specific frame when sending an icon that this can happen just before the Den of Trials costume select menu pops up when everyone gets on the Triforce. A video of this method can be found here:    • Video   (Thanks for uploading that, Mr Salty!)


Update (7/6/16):
This method can only be used in levels, where the start menu is available. An alternate method was discovered that allows you to icon spam anywhere you have access to the icons, like in the lobby and during certain cutscenes, but only under certain circumstances. That method can be found here:
   • Tri Force Heroes - Communication Icon...  
Thanks to nonsense205 for discovering this alternate method.