The chromatic scale is often used for pitch glide and siren exercises.
For a pitch glide, start with a vowel sound like "oh" or "ee" and smoothly slide your pitch through the notes.
For a vocal siren, shut the windows and increase the tempo. Sing "woo" for your best siren impersonation, starting softer at the bottom and increasing the volume as you slide to the top of the scale, then back down.