Remember too though the actual "head" of the microphone that you choose.
Having the "right" receiver, good aerials on both the mic and receiver, diversity (two channels), etc etc etc...are all for "nothing" if the mic makes you sound "rough" or squeals with feedback everytime you're within 10 ft of the front of the speakers.
I use a Shure SM58 diveristy mic... using the two aerials that connect directly to the receiver (14 inches long each), I can walk about 500 metres away (open ground) and I've tested it to about 300 metres through buildings/walls etc... (the signal goes through the walls, not me...!)
Most unusual use, at distance? I regularly get slips of paper from the valets at one hotel that I do, about cars leaving their lights on. So, I nip out to the car park...and announce... "The owner of F542 PRG, a red Golf....you've left your lights on... you've also left 3 empty Snickers wrappers on the floor, cd cases strewn all over the passenger seat, a sat-on packet of Bensons on the back seat... oh and 4 months worth of dust on the dashboard..." etc etc....whatever happens to be there.
I once saw, (and announced) a copy of Playboy in the backseat of an estate car...turns out that the owner was a girl...

Still it takes allsorts to make a world, (and I love those pink and yellow coconut ones

)