Overall I probably have the greatest appreciation for Lateralus, although big fan of all the albums.
Got to see them live for the first time in 2002 in Wellington, which funnily enough coincided with the weekend I saw league live for the first time (Warriors v Bulldogs). Was blown away, right from the Melvins opening, to the weird crazy soundcheck (all kinds of evil creepy noises), to the weird naked upside down people hanging down writhing all contortedly during one of the songs, to the EXTREME loudness.
Also, saw them at BDO '07 (Muse-Tool closer was epically mean) and got to hear one of my favourite tracks Forty Six & Two (which they didn't play in 2002). Cameo by Serj on Sober was also great.
Absolutely looking forward to them again at next year's BDO, even though I'm unaware if they even have new material.
Also love the first two Perfect Circle albums (eMOTIVe, yeah not so much), which I also got to see live in 2004. Which was great, although coincided with a massive flooding the night or two before up and down the country, so they were unable to bring much of their stage show, so it was a rather stripped down & raw show (music still rocked the party that rocks the body).