GAMEPLAY: Fairly linear--I hold the right mouse until I see someone (or they shoot at me before I see them), then spam the left mouse until they're dead. I like the vacuum concept, though, and could see it being quite fun on a larger level with more options and item variety (like what you've done for the ice bucket). That may be outside your scope for this jam, but I could see you taking these mechanics and expanding them later. I died a few minutes in from being shot during an elevator transition, which made me quit the game entirely. Normally, transitions like that give a bit of invulnerability, though you could also try to place enemies to avoid that being possible.
VISUALS: Don't be too hard on yourself--while this certainly isn't professional pixel art, it's got character to it that I like. There's a few odd things: the dialogue isn't fixed to the screen, the font makes 3's and 8's look alike, objects don't fall when partially sucked (the player has gravity, just put some there).
SOUND: Another victim of forgetting to loop music (specifically the menu and tutorial). I almost did this, too. It's a hard one to catch when you're speeding through playtesting, but fortunately an easy fix. Love the choice of noir-style jazz. Not bad choices of sound effects, though maybe I just giggle too much at offscreen glass shattering. I see what you're doing with the vacuuming sounds, which is a good idea, but there seems to be a large gap between "starting" and "continuing".
THEME: Sucking various objects up and spitting them out fits the bill, but you could definitely go further. I was itchin' to hurl a table at someone.