Wow, that's a hard question for me... I really have to give two. In about 2009 I was at the house of two of my cousins, and they and I built practically an army of MOCs I remember we had several Toa (I remember a Toa of Fire, a Toa of Lightning, and a Toa of Ice, but I know there were others), At least two Skakdi (Amusingly, one of them was on the side of the Toa), and several other MOCs. The thing is, most people would probably have considered us "too old," to actually play with them, but we did anyway. The funny part, is this was really the first time those particular cousins had ever really wanted to play with Bionicle sets. Sure, we had role-played as our favorite characters, or sometimes as some of our MOCs, but they had never really cared to use the sets themselves for anything besides building, but after that despite being "to old" they actually started playing with them a lot. The other memory, is of a MOC I built, originally just a generic Rahkshi, except this one was a "good guy." Eventually I broke it down for parts, and then Re-built him a month later. Then broke him down for parts again, and rebuilt him. I built a MOC in 2003, that has "stayed with me" ever since, every time I took him apart, he eventually was re-built bigger and better than ever, and now I have what is probably the final version standing on my shelf. I guess I just always liked the Idea of a "good" Rahkshi.