Not necessarily an acronym, but here’s a fun one for Japanese: Laughing in Japanese is warau, which gets shortened when typing to just w. If you want to laugh a lot, you would type wwww. That ends up looking like a field of grass, so that in turn gets shortened into 草 (kusa, or grass). Basically, 草 is the Japanese equivalent of lol
Also, in Chinese, thank you is often abbreviated as 3q, because when you say it out loud, it sounds like “thank you” (san kyu)
You plan to walk into the counter? Daring strat, but I can see it freaking out the cashier enough to cancel the tip himself if you also maintain eye contact while walking, like an Oblivion NPC