Well he actually did use it ins HL2 (it's attached to the buggy, alyx refers to it as the "tau cannon") In hl2 beta, there was originally a scene where one of the rebels butcher the tau cannon off of the buggy to fight off the incoming combine, with you as the operator. If look at the animations their are still various ones for this scene. Who knows? as the buggy was confiscated by the combine (possibly to be destroyed or, heaven forbid, research the weaponry that has been defeating all they can throw at it thus far.) You might find a crashed dropship with the buggy nearbye some time (maybe hl3 where you play as shepard or something, but that's just a incredibly vague and loose opinionated idea) So you might get to use it some time in the future. If you didn't read all that, then in essence: probably not.
Also, who is this tolkiendil guy, and why does he automatically come up as the guy that answered everything?