Pushers. They force me to practice my approach patterns, use disciplined transition footwork, and stick my volleys and overheads. Against people who miss, even if they hit a better neutral ball, those offensive habits often slack. Half way into the first set against a true pusher, I'll have dialed in that part of my game again, and it's extremely fun. Usually serve-and-volleying at least half the points as well.
Players who can hit hard without missing help me tremendously as well (far more rare, usually UTR 7.5+). They force my swing to refine itself into its more abbreviated version, which performs far better all around the court. Against no pace players, I get lax and have a few hitches that don't need to be there. Those get so punished by people who can actually hit that they quickly abate.
The player I play worst against is the decent velo guy who misses every third ball. I know there's no way I can lose, so it's hard to focus. I make too many errors from the baseline, but I don't really notice, because they're making more, so I'm still winning. I'm never really pressed to go to net, because if I just hit two solid deep topspin groundstrokes in a row, the chance of an outright error is like 80%. Contrast that with the pusher, who FORCES you to play in order to beat them, or the high velo consistent guy, against whom you will lose every single point if your strokes aren't dialed in. The feedback in matches like that is infinitely better.
