Used the least: Mono papillon (the smaller one, but I bought the one with the brown handles, not the regular ones, was that limited edition or something? I did buy it at the LV store, it was my 2nd LV purchase many moons ago when I was young and naive and I knew nothing about LV but I like the bags.) Too small for me now, will use it again later in life.
Most regret buying: Mono mini agenda - too small to write down all my kids schedules and my stuff. LOVED all the stickers though, and the ruler.