Can I get a VAC ban for using BunnymodXT, adding valve_WON and .dll’s to steampipe Half-Life or using non steam Half-Lifes when steam is on or stuff like that?
Yes, you get immediately VAC banned on all games on your Steam account.
[spoiler]Seriously, as long as you don’t connect to any servers, you are safe. Huge number of people is using all this and no one is VAC banned yet.[/spoiler]
Was this serious? 
Instant VAC ban for all these for all games? Heard modifying game files and using some non steams gets u VAC banned (or joining VAC secured servers while steam is on, not sure) so thats why i ask.
[spoiler] Alright thanks ^^[/spoiler]
Some games (whose developers are cool guys) apparently VAC ban you for any kind of modification. However, Half-Life is not one of those games, and moreover, unless you join any server, VAC is not running. Singleplayer is safe.