This post is specifically aimed at Halo 3, but also goes for H2 and Reach:
Starting with the Storm, I noticed a mongoose endlessly accelerating into the Scarab's leg. Wouldn't just back up or drive away -- just endlessly driving into the leg as if it was trying to run the scarab over. I thought it was odd, so I drove my mongoose over, gave them a push, and off they went. Happened again with the Ark. I was gunning for the gauss hog that picks you up after extending the bridge and multiple times the driver just drove me right into the Scarab. Didn't back up or turn. Just kept accelerating as if he was gunna somehow push it over. At this point I was kind of frustrated, so I just hopped in a tank instead. On The Covenant I watched another gauss hog do the same thing. Just kept accelerating into the leg like it was magnetized to it as the scarab itself was in the midst of blowing up and ended up taking the gauss hog along with it. Now I know friendly AI in Halo aren't known for being... good. But I do try and keep them alive as long as possible and watching this happen immediately after getting a checkpoint made me really irritated.
I don't know why the friendly AI just keeps driving straight into the scarab and I don't know why they can't just back up, especially considering that they otherwise immediately start driving away if a scarab is in the process of exploding.
This, along with general improvements to AI driving patterns across the applicable games would be very much welcome. Would anyone be able to tune these at all?