Watch anime of course :D

Watch videos on Youtube or surf forums.

I play games that don't require internet.

play an offline game or just poop around :p

Play other games? XD ...Sleep? XD

It doesn't use all my bandwidth... I can still chat with my friends and surf the net, for example.

What's this entirely used up you are talking about? I never have that here.

i let steam download in the background limiting its bandwidth ;)

Play Games or watch Animes or Movies or do some stuff with friends

make tea. my internet is pretty fast, i can download an average sized game in 10 minutes or so

It usually doesn't use that much of my bandwidth, though I do believe that downloading pauses when you're playing a game on Steam, so a quick match of Killing Floor or TF2 is pretty much out of the question. ._.

Most of the time I surf the 'net, listen to music, tend to the needs of my dogs, or just play a game on a console or another client. Thankfully it doesn't take too long to download things, which is nice. I do hate waiting.
ETA It helps that my download speeds are fantastic!

Take a drink.

sleeping

Warband

I fap to the sexy download speed chart

I go to sleep :3

Playing another game?

Fapsturbate. (Honestly I read manga online, like Hajime no Ippo. I'm near chapter 700 and I like it a lot.)

Sleep, watch TV, go to work, browse the internet, play another game. Whatever I feel like doing basically.

Most games will download in a matter of minutes anyway.

Play another games on another consoles or watch movies :)

playing Minecraft

Play other games offline. Unless I'm feeling pretty tired, in which case I'd go to sleep.

Steam doesn't use all of my bandwidth (not even close), so I pretty much just do whatever, including download other games from other places like Desura...

Just the same things as I do everytime I'm not downlaoding anything. Browsing some sites, chatting with friends, playing games, watching movies/videos all all that stuff.