The banners nobody reports
A GG in block letters takes five rows and two seconds. It is the one chat art that never gets a bad reaction, and after a close match it is often answered in kind by the other team.
This theme also covers the messages for your own side: nice try for the clutch that almost happened, thx team after a good trade, my bad when the mistake was yours. Said in team chat at the right moment, they do more for the next round than a strategy call.
Honest or sarcastic
A GG at 13-2 from the winning side can sting as much as an EZ. If you want it to read as sincere, pair it with WP, or use the heart version. If you want the other kind, the toxic theme is one click away.
Updated
Questions players ask
When should I send a GG art?
At the very end: after the last kill, while the scoreboard is showing. Before that, a GG reads as giving up or as a taunt. GLHF goes at the other end, during the first buy phase.
Which chat should a GG go in?
All chat, so both teams see it: open it with Shift+Enter. Be quick after the last kill, because the chat is only usable for a short moment before the match summary takes over.
What do GG, WP, GLHF and NT mean?
GG is good game, WP is well played, GLHF is good luck, have fun, and NT is nice try. They are the standard courtesies of competitive games and are understood in every region.