I was fighting this Devil Walker alone, for the first time (I suspect because it was about 2am in the UK by then) and I didn't even notice I still had one rocket left. I figured I might be able to finish him off with my fist of havoc, but (as has happened so often) I wasn't able to correctly judge the distance I'd leap upon activation (it seems to depend on whether or not you were sprinting when you jumped — sometimes it'll go directly down, other times it'll leap a bit further forward).

Ah well, I'll get him next time, pesky Devil Walker…!