I gotta say 7s core of kaidus, raymon and thalash (starkie as well but wasn't on every iteration) has gotta be one of my favorites because it was awesome to see one core group of players reform every year and play so we'll together that they actually gave b4nny a run for his money every time. The other teams like nerdrage and full tilt were perhaps more fun to watch because they played so aggressively but I don't think any team stuck together as long or had such a definitive playstyle (albeit a tad slower than my personal liking, it won games). Epsilon was sort of before my time but I'm sure that core group of players had a similar appeal. I think 7 have a special place in my heart though just seeing them at all the iseries lans as well as the two rewinds, their grand finals were some of the craziest games I've seen and watching raymon and thalash play together is definitely a big inspiration to me. The old core of shade, blaze and b4nny was also obviously a huge inspiration as well but I feel like 7 probably takes the cake for 'favorite' just cause they were always the underdogs.
I really enjoyed playing with my boys on velocity and I feel like we kept a good core of people and improved together, but ultimately never really were able to break the 4th place curse which was a shame. Trip, sigh and I have stuck together from the Ford iterations to this season on MAL so that's been nice, always good to keep the calling and playstyles that you've developed and have them carry over without having to start over from scratch with a brand new team.