Some of my thoughts on the matter (many of these have already been noted):
- problematic pump (either too small, leaky, awkward to use, or all of the above)
- poor pressure: either due to an over-active pressure release valve, leaky joints, or weaker CPS chamber, if a blaster feels underpowered for its size compared to other similarly-sized water blasters, it probably is
- restrictive grip region: if a grip is too small or uncomfortable to hold, it detracts from the blaster
- poorly made nozzles: nozzles that spray when supposed to be a stream or vice-versa are annoying
- lack of ease of carrying/refilling: larger soakers should come with shoulder straps both for balance as well as being able to carry around more than one easily if desired; handles on larger soakers are good, too, to aid with stabilizing the blaster when refilling
- poor overall ergonomics: soakers should be comfortable to hold when full, empty, and all ranges in-between. If a soaker is front, rear, or side heavy at different times, this leads to undesired strain when using it
- badly designed nozzle selector: for soakers with nozzle selectors, they should be easy to select and easy to figure out what is selected without needing to look at the front of the blaster
There are more points, but that's what's coming to mind at the moment.
