I've LARPed for over 20 years now at Gencon (OMG does that statement make me feel old.)
Number 1 on my list has been the 7th Sea Game run by Plaid Chamleon Gaming (aka Dana's 7th Sea game) I am officially biased on this one though, I'm helping write it this year.
The Elder Entertainment games ROCK! I did 3 of them last year and can't wait to see what they pull off this year.
I've loved the BYOV games I've been in over the years, especially the year I got to carry a magic wand made of cheese.
Millenium Interactive Gaming has run a wide variety of great LARPs over the years.
As a former TD director I can say TD is not a Larp although it is something worth experiencing at least once.
Trust me, I've been gaming forever.
25 Gencon's and counting
Gencon does not run itself, it takes thousands of volunteers, consider being one
Plaid Chameleon Games