Besides the Delta II and PSLV-G/PSLV-XL, there are a few proposed/in-development stages that would fire 7 engines at once.
Blue Origin’s New Glenn booster is designed with 7 BE-4 engines powering its first stage.
ULA has put forth a paper design for a “Delta Super Heavy”, 6 boosters surrounding the central first stage core of the Delta IV. I don’t know if the idea was for it to be flown with all 7 engines firing together, or if it ever got beyond a vague concept stage. I note that the Delta IV is currently a horizontally integrated launcher, and that going to 4 or 6 boosters would raise difficulties with that strategy.
The Angara family has a proposed A7 configuration with 6 boosters around one core stage; this is likewise unlikely to ever be built.