I'm gonna borrow a few ideas from Orcs Must Die! for suggestions:
Arrow Wall Trap: When triggered, it fires a barrage of arrows forward. Can be done in BL via making the JVS effect spawn arrow projectiles (aka from the bow)
Spring Trap: Something to send a blockhead or vehicle flying when triggered, either upwards or flinging em off to one side. AKA into a pit of DOOOOM.
Smashing Block: A block that smacks downward into the ground. 8x8 for extra pain, maybe even cube sized?
Retractable Axe/Sawblade/Spiky Bits: Your typical 'item jumps out and attack' kind of trap. Similar to the spikes shown in the preview pic, just not, well, spikes.
Trapdoor: Ya probably got one allready, but basicly a trapdoor that drops you into inetivable pit of DOOOM.