Changing pitch over time is a great way to get more mileage out of a recording. Sometimes you have a great recording that you need to use several times in a row, and changing the pitch envelope can trick your ear enough to make it work. It's a great way to make a steady recording have some movement, or create a Doppler shift. Some of the plugins that are designed to do this (i.e. Waves Graphic SoundShifter) leave too much of a footprint behind, and led me to a few cleaner alternatives.
(Note: when recording your own sound effects, record at the highest sample rate you can to preserve the resolution if you plan on slowing the recording down significantly)
1. ProTools "Vari-Fi" with Selection Length
We all know Vari-Fi is great at delivering tape-machine-style "slow down" or "speed up" effects, but the effect can be heavy-handed and the lack of control is frustrating. The good news is the plugin works over time across the length of your selection, so you can milk some functionality out of it by changing the way you select the region you want to effect. In most cases, if I select the entire region the effect is a little too intense (Fig.A), so I tend to experiment selecting more silence before and after the region (at different relationships) to achieve the desired effect (Fig.B).
2. Reaper's Pitch Envelope
Reaper has a great built in pitch envelope (Fig.D) that allows you to draw in automation with the mouse (more fun with a Wacom tablet if you have one...). The pitch can raise or fall 3 semitones from the center line in either direction (Fig.E). Doesn't sound like much, but any more than that would probably leave behind unwanted artifacts. Reaper has a 60 day evaluation period, and is only $60 for individuals after that.
3. Recording from Soundminer's Pitch Slider
This method is one of my last resorts. I mostly use it to achieve an extreme or cartoony effect. We are basically going to use SoundMiner as an instrument, and perform the desired pitch change using SoundMiner's pitch slider, while recording its output into another track.