Use PowerPoint to create giant letters in any font. Use pictures, textures, or color to fill to fit any theme. You can also print out on bright paper (and laminate) for cheap and durable bulletin board letters. Great way to have just the letters you need.
Try to use dots, stripes, lines, curls, italics, bolds, underlines, and different sizes to create your own specific tone and technique. Doing something casual and neat for a friend can include a lot of different types of lettering