Being chained to Billy while climbing a rope still sometimes breaks your model as of writing this.
Billy geometry is funky making is difficult to shoot while standing in front of low hand railings (Billy shoots his bullets much lower then where his gun is).
When Billy ulting if you ramming charge into someone and immediately slam as your ult goes off or ramming charge into slam and immediately ult, Billys FOV will expand aggressively, ive seen it shoot way past 5000% once. Billy FOV will expand in the same way if you slam or ult right after jumping off the lane wire at fast speeds. (this is common in later games but difficult to recreate in sandboxes).
Billy reload animation while crouched as has some obvious rigging errors with the gun floating far out of his hand.
Chain Gang gets turned off when using Ethereal shift or riding the lane wire. Blasted is unaffected by these two so it is unclear if this is intended.
When Billy is in an idol stance his gun is pointed up, shooting will look like the gun was shot in the air despite bullets coming out of Billys chest.
In very rare situations right after person x has gotten out of a stun, person y can heavy melee and phase right through person x.