There are several categories of offenders and here is my list in no particular order. What we need is a supermarket task force to police these offences and issue on the spot fines or even in serious cases expulsion from the store.
The aisle hog - need I say more? Stick to the appropriate side and if you stop allow for people to go around you. Meaning if someone else has already stopped exactly opposite to you ....isn't it obvious you have just illegally parked?
The stop and have a chat and block the aisle - this is a similar offence to the above however it is far far more heinous because you are holding people up for a reason that isn't even shopping related. Not to stereo type here but I find the worst offenders to this cardinal sin the senior citizens.
The people that try to sneak through the express 15 items or less lanes or self serve scanners with whole trolleys! - Can people not count? Or are they just confident no one will have the guts to confront them. Where is 'super[market]man' when you need him?
The people that are already at the check out and run for a forgotten item - I think that everyone has been guilty of this one. Even me with my superior Virgo organisation skills. But we must all collectively try to be better at this by shopping from lists. My parents have the most organised system in the world. They have a list on the computer of all the items that they ever buy (its even in approximate order of the aisles) they print this list weekly and leave it on the fridge and highlight items they need to buy and my dad takes this to do the shopping with him. I know we can't all be as obsessive as my parents but its a goal to strive for.