Knives in MOST cases are ONLY allowed if they are rubber (maybe even plastic).
I myself have a Real steel M9 Bayonette for show + Survival tool but for A/S ONLY my Rubber M9 is drawn.
Shields are rarely used in Outdoors games. Realisitcally soldiers dont carry a shield on their back when they are on a field. CQB or indoor games they may be accepted, but you should ask the organizer first, because its their say wether its a go or nogo.
As for props, anything usually is a go, however you should be aware, props weigh too, and from my experience (cause im a gearwhore) All that useless gear weighs you down.