I had a few, some not really weird:
Back in the middle of 2014 I just finished crafting my Ember and I was happily trying to level her up on a defense mission on Earth. Turns out I got grouped up with a really loud speaking dude that I assumed he was a twitch streamer, but he clearly knew nothing about the game. It was pretty funny to listen to him shout orders in a less than polite way, mention how shitty the enemies were and stuff like that. I lost my shit, however, when I was almost dead and rolled towards a Fire Eximus, which promptly cast its fire nova skill on my face and downed me. Streamer guy came to my help and was baffled: "WHAT THE FUCK EMBER HOW DO YOU EVEN ULT AND DIE LIKE THIS?!"
Grouped up with some brazilians, who proceeded to trash talk (in portuguese) and troll me using Loki's switch teleport and Valkyr's rope around the level. The funny part is that I'm brazilian too, but my IGN doesn't make that obvious, so I played along and politely asked them (in english) to stop fucking around with me, but that didn't work at all. Text and voice chat clearly showed me they could understand me but they kept doing that for teh lulz. Only after I got tired of that, I spoke to them in portuguese and they finally stopped being dicks.
A guy I met several times when farming in Eris. I was trying to make conversation and he just replied "stfu". After a long silence he blurted out "I no speak english good". Alright, I tried asking him what language did he prefer to talk in. Worst case scenario I could open a google translate tab, so I asked "French? Spanish? Portuguese? Russian?" and he just went back to "stfu retard". I met him a few more times later and greeted him as the 'stfu retard guy', and he replied exactly the same thing. Until one day after I greeted him and he started to talk about the game, using a very broken english, but that was enough to go on using the names of stuff in game. We discussed about our favorite weapons and frames, favorite maps and a few strategies too. TL;DR: "stfu retard" guy turned out to be a cool guy.