Gigabyte makes some of the best value gaming monitors on the market, and today their popular G34WQC ultrawide is even better value than normal. This 34-in monitor has been reduced from $450 to $400 on Amazon, an excellent price for a monitor of this size and quality.
In terms of the specs, the Gigabyte monitor comes with a 34-in curved VA panel, with a 3440x1440 (21:9) resolution and 144Hz refresh rate. The monitor meets the DisplayHDR 400 certification, meaning it can accept an HDR signal and get reasonably bright (500 nits) to offer good contrast (~3000:1) between dark and light areas. Colour accuracy is also a strength, with coverage of 90% of the DCI P3 gamut and exceptional Delta-E values that makes this a great choice for colour-accurate work (if you have a colourimeter on hand to calibrate it - otherwise it's merely good).
The G34WQC is also a FreeSync Premium and G-Sync Compatible monitor, so you have a low-lag solution for tear-free gaming no matter which graphics card brand powers your PC. There's also a (somewhat rare) Black Frame Insertion feature that improves motion clarity, which can be great for games that run at high framerates. In general, this is a well-equipped monitor that gets great critical reviews and averages five stars on Amazon as well - not bad!
So what about alternatives? Ultimately, there are monitors out there that can get brighter, or operate at a higher refresh rate at the same resolution, but these models tend to cost considerably more - for example, the Odyssey G9 is amazingly immersive in ultrawide games, but oft retails for four figures. This 3440x1440 144Hz spec really is the sweet spot for ultrawides right now, and $400 is the best price I've seen for a very long time. The only similar monitor I can find is the admittedly good AOC CU34G2X, which looks to use the same 34-in panel, but it's $50 more expensive!
So - if you're mulling a monitor upgrade, consider the G34WQC. At $50 off its normal price, this is an awesome time to pick one up.