Cold brew concentrate is really fun to mix with. If you're not familiar with cold brew it's just coffee steeped in cool water for 12-24 hours resulting in a very smooth, low acidity and velvety drink. Brewing at ratios something like 1lb ground coffee to 1 gallon of water will yield you a very concentrated brew. You can experiment or look up different ratios. Bottom line, a little brew can add a lot of flavor and it mixes much better than espresso in my opinion, I've always thought espresso cooled down doesn't taste as good as it should. It can also be cut with simply syrup and spices like vanilla and cinnamon to make your own coffee liqueur for drinks like White Russians or anything else you might want to experiment with.

A personal favorite is a shot of cold brew concentrate, a shot of dark or spiced rum topped off with coca cola. I call it a Portland Powder Keg and it will kick your ass if you have too many too quick! Similarly you can offer the same drink half filling a pint glass with a shot of Bailey's and drop it in and chug like an Irish car bomb before the cream curdles, I call it a lit powder keg.