What can I get on the sale for under $2?

Brothers - A Tale of Two Sons - $1.49 (one of my favorite games of all time)
Antichamber - $1.99 (one of my favorite games of all time)
Harvester - $1.49 (if you like old point and click games with FMV)
To The Moon - $1.49 (haven't played yet)
Fez - $2.49 (liked it a lot)

Some of these sales end in as little as 9 hours from now if you are interested.

Just because these are some of my favorite games doesn't mean everyone will like them, but i'm sure you can watch the trailers and get a good idea if it will be the type of game you are into. They are all highly rated games, especially the first two.

These are the only two that come to my mind that are not bundle games:
Blade Kitten 1,49 euro
Half Minute Hero: The Second Coming 2,49 euro
Shadow Warrior 2,49 euro

Nothing and whatever you can you don't want to. The thing you might want are cheaper in bundles or trough trade.

A Serious Sam game, A Half-Life game, Brothers: A Tale of Two Sons, 140, A Flatout game, MirrorMoon EP... there are good choices there...

Step 1: Wait for the original Deus Ex to go on a flash/daily deal alongside the one you already own. It'll be at least 75% off, maybe more.
Step 2: Buy it.

If the graphics from 2000 don't put you off, you'll pick up one of the ten best video games I've ever played. And no, I'm not going to qualify that with "PC game" or "classic game" or anything. And I'm not just talking from nostalgia here either, because the first time I ever touched the game was less than two years ago. No joke. Top ten.

Shadow Warrior is on super sale

Best site i found in terms of tracking of all steam sales:
https://steamdb.info/sales/

You can chose according to your budget and preferences, as you have them all on one page:)