Never ever use the mini-sentry on defense. In all other situations, it kicks ass, especially if you combine fire with your shotgun and pistol (never use the wrangler with the mini-sentry).
I'm appalled you guys actually thought the thing was...
useless! You do realize that it starts with full health the second you put it down, right? It's not like the normal sentry that can be killed in one shot when it's building. Just spam the little buggers offensively with your team and there will be hardly a thing their team can do about it. For example, on Badwater, set up a teleporter for your team, then as your team makes a push, destroy your mini-sentry and put up a new one some place where it can target a lot of enemies (such as the big ledge), and shoot anybody who comes near (the sentry will usually automatically target them as they approach as they target the closest enemies, so you'll know they're coming. The second it gets destroyed, just pop down another one. You won't believe how many kills and assists you get off your dinky little half-damage level 1. If you can deal with the tiny clip size on the FJ, you can rack up a TON of revenge crits by putting a mini-sentry some place where it will attack from a direction the enemy isn't looking because they're fighting the rest of your team. Personally, the shotgun is my favorite weapon in the game and -3 shots is far too big of a downside for me to ever use the FJ.
Edited by MafiaGuy7, 02 September 2010 - 02:32 PM.