This card at base seems a little underwhelming until you follow their design philosophy.

If you're playing this as a straight guardian, you should note you'll get a free action when you play it and another when it leaves play. That alone is basically two free actions, which indeed seems worth the cost of 4 exp (after all, Ace in the Hole is 6 exp for 3 actions). You just need to make sure that both the entry and exit fight are used, and it will drop off in value if they aren't.

Where this card starts to become dumb is sleight of hand. Using sleight of hand to play this gives you five attacks in one round, and you get the gun back. That starts making the value of the card shine through.

Its overall a pretty good card. It appears underwhelming at first, but if you build around it and maximize its uses it does become a nifty weapon.