As was said, its pretty easy to make a water solution from tobacco, and spray it on plants. Enough nicotine will poison aphids, as an example. I'd even heard of people used this sort of stewed tobacco as a wood finish.
Please be careful, especially when spraying, you can inhale or otherwise ingest, enough nicotine, by this method to injure or kill yourself. No, I don't gradually like a smoker, I mean, hospital trip and you die there.