First Impressions

When you see a person's gear: What is the first thing that comes to mind about them?
Me?

Rapier - "BS fisher"
Giant and/or Havel - "Common ganker"
Giant and/or Havel w/ large weapons and fat rolling - "Has no idea what they are doing"
Stone Greatsword - "This one is smart"

Of course I say first impressions because these are only my stereotypes and I will admit I have actually used these before without being any of the mentioned above.

be wary of those fat rollers with str weapons, a lot of times they are actually really good.

To me honestly when I look at an invaders weapon selection the first thing that comes to mind is the counter to them. To me I judge their movement when I see them circle then for the most part they are fishing for BS but sometimes not. It can take about ten to 20 seconds to gauge exactly what their play style may be because its at this time they start to use 2nd hand weps that will reveal more about their intentions. And I agree with you on the stone sword lol. They be smart players who use that and in my opin the dangerous kind. I usually get my BS warning ringing loud and clear on buffers though, especially those of the great demon axe variety lol. The only time I am certain about BS fishers are with the dagger users. Just my opin.

i normally shudder at the sight of a BKGA, popular choice of ganker and apart from that, probably my least favorite weapon to fight, i often loose to it....
but yeah, armour choice generally a give away, but seriously, getting sick of invading, first thing to happen, opponent starts circling....!!!! SO ANNOYING!!!! recently been using BKGS and I just R1 spam and catch them every time, 99% of circling bs fishers either wont try a parry or will FAIL and get flattened.....
also, I tend to underestimate people wearing elite knight set pieces i think, for some reason i assume noob, but they are actually good armour pieces worth wearing.... :/

Never underestimate the fat guys! I usually have to hit them like over 10 times to bring them down with my scythe when they only need 3 hits to kill me

I never assume they are going to be newbs. But, I do look at builds to figure out their main strategy. BKGA Giant MoM? BS fish or R1 spam. GC? Roll R1. Spear? Pokey pokey. Etc