Through what ways can TNT be ignited?

After the 1.7 update where you cannot ignite TNT with your bare hands anymore, what are the other methods of igniting it? and also important can Creepers ignite TNT?

TNT can be lit by fire.

TNT ignited by fire

Lightning striking on the ground at Medium difficulties and up causes short-lived fires which may be able to trigger an explosions. I haven't been able to test whether lightning directly striking a TNT on Easy or Peaceful will still trigger the explosion.

Lava also causes TNT to ignite as the TNT catches fire because of the Lava. So does lightning if it strikes your TNT, it also causes the TNT to catch fire and it will eventually ignite.

TNT can also be ignited by a Redstone Pulse send out by a Redstone Torch, Button, Lever, Pressure Plate or Detector Rail. This is also the most common and safest method as it doesn't accidentally burn any flammable materials near you.

TNT can also be lit by left clicking it while holding flint-and-steel. In creative mode you must use right-click, otherwise the block is destroyed.

Another source of TNT triggering is explosions. TNT can trigger more TNT, as well as creepers, ghasts or exploding beds in the nether.

Yes, creepers can ignite TNT. When a creeper explodes within range, the TNT will detonate instantly.

TNT or creeper explosions will trigger TNT. I'll bet every nickel I have that Bed, Ghast, and Blaze explosions do it also, but can't test that easily right now.

If you set fire to TNT or if fire spreads to TNT it will trigger it. This means lava can ignite TNT..though remember the TNT needs to have one of its six sides free so that the fire can spread to it; a TNT block entirely submerged in lava or surrounded by blocks will not ignite.

If you are holding flint and steel and you punch (left click) TNT it will ignite. This is the cheapest way to ignite TNT because it will not diminish the flint and steel's durability.

Redstone current will trigger TNT. The easiest way to use this is to make a lever (one cobble block, one stick, easily craftable without a table) and set it off using that.

I've tested all the above, and you can do so too easily by popping into creative mode or a test world.