A hotkey to increment values up/down by 1 would be very useful in some situations. Particularly when building inventory lists in console style RPGs that use the memory address to reference an item table. It would come in handy for a number of other bizarre memory hack situations I get into but this is the simplest one to give an example of.
Take The Last Remnant (PC) for example. Let's say I manage to isolate the main character's primary weapon at address 1AAC0000 as a short. If I set the value to 98, I get a Broadsword. If I set it to 286 I get a Ninja Katana. 821 a Cudgel. So on and so forth. In this game's case, there are at least 1361 valid numbers for an equipped item address. While it's possible to locate an unknown item without a base reference point by manually adjusting values the long way one point at a time, it's very time consuming.
Usually do this sort of thing to get around hard coded limitations in various games and go with really crazy custom setups. Sometimes, it doesn't even crash the games. If there's already a feature that does this, sorry! Tried to look through, couldn't see anything that pointed to it.