Do you have suggestions for simple/cheaply made props for a sci fi/fantasy themed

[cruelkitti]

party? I'm having a sci fi/fantasy themed party in late October...featuring 9 bands food vendors etc etc. The last one I through had over 300 people in attendance (it was zombie apocalypse themed) but the prop ideas were endless and easy and fun...Now I feel like I have to have as impressive if not BETTER props and decorations that the zombie show...Any ideas? I like corny stuff/serious stuff/ ridiculous stuff...humor or gore...pretty much anything that goes hand in hand with sci fi and/or fantasy...(think aliens/robots/unicorns)