One of my favorite nodes is the super fast pointgenerate. I use it all the time as foundation for efficient workflows and HDAs.
Matchsize is another beloved one, although I noticed it too, it could be faster if converted to pure Vex.
Enumerate is another little gem, extremely helpful in re-enumerating spare pieces that have non-continuous indices. (I would like to understand the algorithm behind this, because I tried to do it in python and it was very slow)
And finally I should assign a mention of honor also to the Connectivity Sop, which I take it for granted now, but the very first times its usefulness was probably mind blowing for me