In the interest of full disclosure, I am running shabbymod on a rooted phone. All these apps should work fine with a stock Prevail though.
Of course there's superuser, a must for any rooted phone. Allows your apps with root functionality to do "root" stuff.
https://market.android.com/details?id=com.noshufou.android.su&feature=search_result
Unified Remote:
Allows you to control your computer through wifi or bluetooth. Has some really cool features like bluetooth mouse/keyboard, windows media remote, and a whole bunch of other stuff. The free version works just fine. Only catch, you have to install a "server" on you pc, so doesn't work like a true bluetooth remote, etc. Still awesome though
https://market.android.com/details?id=com.Relmtech.Remote&feature=search_result
Missed Message Flasher:
Because the Prevail doesn't have an LED, if you miss a call or message you won't know unless you unlock your screen and check your phone. Solution? MMF. Highly configurable, free version works great. Worth buying to support the developer though.
https://market.android.com/details?id=com.tomatox.missedmessageflasher&feature=search_result
Juice Defender:
There are a lot of battery saving apps out there, not sure which one is the best, but this one works great with the Prevail. Probably the best feature of this one is that it turns your wifi on and off automatically depending on whether it detects a network you can connect to. Saves me the hassle of turning it on and off. Also has some cool features like restricting autosync, and turning data off when the screen is off. The free version is okay, but you have to buy the full version to really customize it.
https://market.android.com/details?id=com.latedroid.juicedefender&feature=search_result
Just Shake:
Just found this one and I'm crazy about it. MIUI music has a cool feature which allows you to skip tracks by shaking the phone. The problem with MIUI is that it doesn't integrate with google music or voice search. Solution? Just Shake allows you to do the same, but also lets you answer calls and skip tracks with your volume buttons. Free version is fully featured, but full version is only $.99
https://market.android.com/search?q=just+shake&so=1&c=apps
Dolphin Browser:
Best browser I've seen. Must faster than stock, and I think a bit faster than firefox, with similar features. Opera is good too, but this one has much more features. There is also a mini version if you don't like to do fancy stuff on your phone.
https://market.android.com/details?id=mobi.mgeek.TunnyBrowser&feature=search_result
Fast Burst Camera:
Unfortunately, the Prevail's camera is pretty basic. I find it hard to get a good picture, especially without the autofocus. Burst Camera takes a bunch of pictures in quick succession, increasing the likelihood that one will come out right. The free version works fine, but I think they are going to start doing ads.
https://market.android.com/details?id=com.spritefish.fastburstcameralite&feature=search_result
Call Announcer
I had the incognito before I got my Prevail, and it had this really cool feature which would announce who is calling or texting you. You can add this functionality to the Prevail with Call Announcer. Its too bad the Prevail didn't come with this feature built in, but the cool thing about Call Announcer is that it is highly configurable. You can even configure it to read your text messages, but I haven't tried that yet. Free version works great. The only real difference is that you can't turn off your ringtone in the free version.
https://market.android.com/details?id=com.codeansoftware.callannouncer&feature=search_result