I may not be an ISFP, but I have a really close ISFP friend. Based on her descriptions and narratives about him, I'm almost sure that the guy she's dating is an ESTJ. She absolutely admires the way he supposedly has goals and the way he's so straightforward and strict about a lot of things. Though debatable, this guy seems to like my friend a lot as well. I'm assuming that this is due to my ISFP friend always being so compassionate and relaxed and this ESTJ guy probably likes the idea of loosening up a bit.
Worst match....hmmm, probably an INTP? That's just a guess, though. I mean, INTPs are the direct opposites of ISFPs based on the cognitive functions of the two. Their way of thinking and processing information is said to be in opposite ways. It's probably true, too. I don't see much balance between these two types. Based on experience, my INTP friend and ISFP friend don't get along very well.