I'm using few different spectrum analyzer which i check peak frequency and equal rms,phase checker,clip vu's (analog and digital),
I defenetly trust my ears, my monitors and my room, but when i master i feel i have a very big responsebility to the client, and i prefer to chek miself with meters and few types of headphones to be sure i've done it just right , some times i even chek miself with a 20$ computer speakers or if i'm doin' a live gig before i have to hand the master to my client i'm takin' it with me to another test .
Mastering is a very serious buisness and i prefer to leave the romantic arguments about algorithms reliabuility out and use them ,not rely on them , but using them because they are very powerfull tools