Card: R5-K6 (2)
Card Text: After spending your target lock, roll 1 defense die. On a <evade> result, immediately acquire a target lock on that same ship. You cannot spend this target lock during this attack.
Usage in game: Maintaining a Target Lock on particularly tough nuts to crack.
Quick Take: R5-K6 is a good droid to stick on an Rebel ship if you've got a few extra points and you plan on playing said ship offensively. He's not going to produce a massive difference in your damage output or anything, but as it's fairly uncommon to one-shot kill a ship in this game with anyone short of Wedge or some very lucky rolls, possessing a potentially persistent (look at that alliteration there! Whooo me!) Target Lock is a pretty handy ability to have at your disposal.
However, this isn't a done deal kind of agreement here. You only get the Target Lock if you successfully roll an Evade result on a Defense die after you spend the Target Lock token. So what's the odds of that happening? 3 in 8, or 37.5%. Not great odds, but considering it doesn't cost you an Action- just happens automatically, it's not bad for 2 points.
So the downside is you sort of wasted 2 points to do something you can do for free in the Action phase anyway. The upside is if it triggers, you can Focus with your normal Action instead. That's not bad at all if you really didn't have bigger plans in mind for the Astromech socket to start with.
Again, there are folks out there who will tell you that having points in your list that aren't utilized 100% of the time is inefficient. They're correct to a certain extent, but as having Initiative lends a fairly nebulous and convoluted advantage, if I were looking at a list that was 98 points that included a ship with an empty Astromech socket, I'd consider R5-K6 for sure. You also kind of have to take into account that line of "wasted points" thinking works a little differently in X-Wing than most other miniatures games because not all ships have the same access to upgrades.
I've seen people advocate the use of R5-K6 on Dutch Vander because the two card abilities dovetail in a rather interesting (and FAQ legal) way. I'm not saying it's a bad idea, but I think Dutch Vander is enough of a priority target these days, I'd be more likely to give him a droid that helps to mitigate damage in some way. If you're curious about the particulars of that interaction, check out my article on Dutch.
Personally, I like using R5-K6 on a X-Wing of the Rookie or Red Squadron persuasion. If I know my opponent usually runs a roaming, loner type ship like Vader or Backstabber for example, I'll have that X-Wing with R5-K6 go after that ship in particular. Having a Target Locked X-Wing breathing down your neck who has a nearly 40% chance of getting that TL back for free isn't anyone's idea of a good day. Look at it this way, if he turns around and deals with that X-Wing, well, he's not going after Luke or Wedge or one of your other higher priority targets. If he doesn't deal with him, there's a better chance of putting some damage on him than there is with just a stock X-Wing. In my book, that's worth a couple of points.